y 


7 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 


>    '* 


' 


PAPERS 


COMPARATIVE    MERITS 


CATOPTRIC  AND  DIOPTRIC  OR  CATADIOPTRIC  SYSTEMS 


LIGHT-HOUSE  ILLUMINATION 


AND    OTHER   SUBJECTS   RELATING   TO 


AIDS    TO    NAVIGATION 


COMPILED  FROM  BRITISH,  FRENCH,  AND  UNITED  STATES  REPORTS  AND 

AUTHORITIES,  FOR  THE  USE  OF  THE  UNITED  STATES 

LIGHT-HOUSE  ESTABLISHMENT  SERVICE. 


WASHINGTON: 

GOVERNMENT    PRINTING    OFFICE. 

1861. 


Tc 

377 


TABLE    OF    CONTENTS. 


1.  Papers  on  the  Comparative 

Merits  of  the  Catoptric  and 
Dioptric  Lights  for  Light- 
houses, (British  Parliamen- 
tary Eeport  of  1857) 1—40 

2.  Plan  for  distinguishing  Sea- 

coast  and  other  Lights  by 
Occultation,  by  CHARLES 
BABBAGE,  Esq.,  &c.,  &c., 
&c.,  London 43—57 

3.  Letter  from  LEONOE  FBESNEL, 

Divisionary  Inspector  of 
Bridges  and  Koads,  and 
member  of  the  Light- 
house Commission,  to  Lt. 
Thornton  A.  Jenkins,  U. 
S.  Navy,  Secretary  Light- 
house Board,  Washington 
City 58-61 

4.  Letter  from  L.  BEYNATJD,  En- 

gineer-in -chief,  Secretary 
to  the  Light-house  Com- 
mission, charged  with  the 
direction  of  the  service, 
Paris,  France 61—66 

5.  Letter  from  HENBY  LEPAUTE, 

Constructor  of  Lens  Appa- 
ratus, Paris,  France 67—71 

6.  Letter  from  T.  LETOTJENEAU, 

Constructor  of  Lens  Appa- 
ratus, Paris,  France 71—77 

7.  Letters  from  WILLIAM  LOED, 

B.  N.,  Marine  Surveyor  to 
the  Port  of  Liverpool,  Eng- 


land 


77-84 


8.  Letter  from  THOMAS  STEVEN- 

SON, F.  B.  S.  E.,  F.  E.  S. 
S.  A.,  Edinburgh,  Scot- 
land  

9.  Proceedings  of  the  Northern 

Lights  Lens  Committee.. 

10.  Letter  from  Sir  DAT«D  BBEWS- 
TEE  on  the  Dioptric  System 
of  Light-house  Illumina- 
tion... 


85—90 
I 


90—95 


11.  Letters  from  Messrs.  ALEXAN- 

ASUKR  MITCHELL  &  SON,  on 
Screw-pile  Foundations  for 
Light-houses  and  Screw- 
Moorings  for  Buoys,  and 
accompanying  papers.  .95 — 99  &  188 

12.  Eeport  on  Lightning  Eods  for 

Light-houses,  by  M.  FAB- 

ADAY,  London 100 — 101 

13.  Irish  Lights,  (Extract  from 

Senate  Document  No.  488, 

1st  session,  2  9th  Congress) .  1 01 —103 

14.  Eapeseed   Oil 103—110 

15.  EefugeBuoy  Beacon 110 

16.  Letter  from  JACOB  HEEBEET, 

Secretary  to  the  Trinity 

House,  London 113—118 

17.  Eeport  of  Hon.  E.  J.  WALKBE, 

Secretary  of  the  Treasury, 
Extracts  from,  on  Improv- 
ing the  Aids  to  Navigation 
in  the  United  States 118-123 


96£7GO 


TABLE  OP  CONTENTS. 


18.  Report  of  Lieuts.  THORNTON 
A.  JENKINS  and  EICHARD 
BACHB,  U.  S.  Navy,  to  the 
Secretary  of  the  Treasury, 
August  5,  1846,  Extracts 


from, 


123—154 


19.  Comparison  of  the  two  sys- 

tems of  Light-house  Illu- 
mination, by  LEONOR  FRKS- 
NEL,  &c.,  &c.,  &c 155—175 

20.  Light-house  service  of  France  176 — 188 

21.  Captain  CANFIELD,  U.  S.  Topo- 

graphical Engineer's,  plan 
for  giving  warning  of  the 
extinction  of  lights 189 

22.  Mr.  ALEXANDER  SxEVENSON.on 

Light-house  Illumination, 

Extract  from  Treatise  on.  190—221 

23.  An  account  of  the  construc- 

tion of  the  light-house  at 
Havana,  Cuba 221—234 

24.  Report  of  the  Chamber  of 

Commerce  of  New  York  on 


PAGE. 

Lights  and  other  Aids  to 
Navigation 234—240 

25.  The  Electric  Light,  by  Mr. 

FARADAY,  &c.,  &c. ,  &c., 
Royal  Institution  of  Great 
Britain 240—244 

26.  Light  dues  levied  on  the  ship- 

ping of  the  United  States 

in  Great  Britain 244—252 

27.  Report  of   the   Light-house 

Board,  March  13,  1858, 
comparing  the  economy  of 
the  present  system  in  the 
United  States  with  the  old  ' 
one,  embracing  a  period 
of  5|  years  under  each  sys- 
tem of  management 252 — 271 

28.  Letter  from  LEONOR  FRESNEL, 

&c.,&c.,&c.,  May  7,  1861, 
to  Commander  Thornton 
A.  Jenkins,  U.  S.  Navy, 
Secretary  of  the  Light- 
house Board,  Washington 
City 272 


CATOPTRIC  AND  DIOPTRIC  LIGHTS. 


BRITISH  PARLIAMENTARY  REPORT,  1857. 


CATOPTRIC  AND  DIOPTRIC  LIGHTS, 


PAPER   BY   MONS.    LEONOPv  FRESNEL   ON   THE    OLD   AND   NEW   SYSTEMS   OF 
LIGHTS  FOR  LIGHT-HOUSES. 


[REPORT  of  Lieut.  THORNTON  A.  JENKINS  and  Lieut.  RICHABD  BACHB,  U.  S.  Navy,  "On 
Improvements  in  the  Light-house  System  and  Collateral  Aids  to  Navigation." — Senate 
Doc.,  1st  session  29th  Congress,  No.  488,  August,  1846,  page  12-1.] 


After  having  balanced  the  advantages  relative  to  the  two  systems 
of  lights  in  view  of  their  useful  and  economical  effects,  I  ought  to  con- 
sider them  with  reference  to  their  security  and  the  facility  with  which 
they  are  served. 

I  will  reproduce,  upon  this  subject,  the  observations  inserted  in  a 
memoir  of  the  20th  of  April,  1830,  in  which  I  replied  to  the  ques- 
tions which  were  addressed  to  me  by  the  government  of  Sweden 
and  Norway,  in  relation  to  the  necessary  measures  to  be  taken  to 
improve  the  lighting  of  its  maritime  coast  : 

"The  service  of  lenticular  lights  is,  in  the  aggregate,  less  labo- 
rious than  that  of  the  reflector  lights.  The  first  demand  at  all  times 
during  the  night  the  unremitted  attention  of  the  keeper.  If,  for 
example,  the  central  lamp  should  become  extinct  during  the  absence 
of  the  keeper  from  the  lantern,  or  while  he  is  asleep,  the  horizon  of 
the  light  would  remain  some  hours  plunged  in  total  darkness,  and  the 
greatest  objection  which  has  been  urged  against  our  new  system  of 
illumination  is  the  fear  of  such  accidents.  Happily  an  experience  of 
seven  years  has  dissipated  that  fear,  and  the  lenticular  lights  have 
been  distinguished  up  to  this  time  by  the  regularity  of  their  service. 
However,  every  precaution  has,  besides,  been  taken  to  replace 
promptly  the  lamp  or  its  burner  in  case  of  extinction.  The  extreme 
simplicity  of  the  day  duty  compensates  the  keepers  for  that  to  which 


they  are  subjected  during  the  night.  To  snuff  and  replace  the  wicks, 
renew  the  oil,  sweep  the  chambers  of  the  lantern  and  the  stairs  of 
the  tower,  dust  the  apparatus,  and  sometimes  wash  with  a  little 
spirits  of  Avine  the  tarnished  spots  upon  it,  and,  lastly,  to  wipe  dry 
the  glass  of  the  lantern  ;  such  is  the  principal  daily  duty  which  is 
divided  between  the  keepers  of  the  new  lights,  and  which  rarely 
occupies  them  more  than  two  hours." 

Opinions  thus  expressed  fifteen  years  since,  based  upon  an  experi- 
ence of  seven  years,  have  been  greatly  strengthened  up  to  the  present 
time,  embracing  a  period  of  twenty-two  years  since  the  establishment 
of  the  Cordouan  light,  and  sustained  by  the  results  daily  offered  of 
more  than  one  hundred  lenticular  lights  of  the  three  first  orders, 
established  along  the  coasts  as  well  of  France  as  of  different  foreign 
powers. 

In  this  important  point  of  view,  then,  the  question  seems  to  be 
irrevocably  settled,  and  I  Avill  only  add  a  few  considerations  relative 
to  the  application,  more  or  less  exterded,  which  may  be  made  of  the 
new  system  of  illumination  to  the  vast  maritime  coasts  of  the  United 
States. 

FIRST.  It  has  been  objected  that  it  would  require  too  great  sacrifices 
to  be  made  to  procure  in  that  country  keepers  possessing  the  amount 
of  intelligence  requisite  for  the  superintendence  of  lenticular  lights. 

SECOND.  That  from  distant  points  or  stations  the  necessary  repairing 
and  renewing  of  the  mechanical  lamps  would  be  attended  with  great 
difficulty. 

I  will  reply,  with  regard  to  the  keepers,  that  the  difficulty  of 
obtaining  proper  persons  to  fill  these  subaltern  stations  appears  to  be 
most  singularly  exaggerated.  In  France  they  belong  almost  al \vays 
to  the  class  of  ordinary  mechanics,  or  laborers,  who  make  from  1.50 
francs  to  2.50  francs  (27  to  46  cents)  per  day. 

Eight  or  ten  days  will  suffice,  ordinarily,  to  instruct  a  light-keeper 
in  the  most  essential  parts  of  his  duty,  receiving  lessons  from  an 
instructor  conversant  with  all  the  details  of  service;  and  two  instruct- 
ing officers  will  be  sufficient  to  prepare  keepers  for  all  the  lenticular 
lights  which  could  be  successively  established  upon  the  coasts  of 
North  America.  The  information  thus  imparted  would  never  be  lost, 
and  these  officers  might,  besides,  be  aided  by  foremen  or  assistants, 
who  could  supply  the  place  in  case  of  necessity.  In  defence  of  this 
assertion  I  will  cite  the  example  of  the  administration  of  Norway  and 
Sweden,  which,  after  having  obtained  the  assistance  of  a  French 


5 

agent  to  put  up  the  apparatus  of  the  two  first  lenticular  lights,  which 
were  sent  from  Paris  in  1832  and  1836,  has  provided  since,  without 
any  foreign  assistance,  for  the  placing  as  well  as  the  organization  of 
the  service,  of  all  the  lights  of  the  new  system  which  it  has  succes- 
sively established. 

With  reference  to  the  eventual  repairs  of  the  mechanical  lamps,  it 
is  to  be  considered — 

FIRST.  That,  in  consequence  of  the  great  strength  of  the  pieces  of 
which  the  new  model  of  mechanical  lamps  is  composed,  they  will 
perform  well  for  a  number  of  years  without  requiring  anything  more 
than  a  proper  attention  to  their  cleanliness. 

SECOND.  That  the  ordinary  assortment  of  a  dioptric  light-house 
comprises  three  of  these  lamps,  which  afford  a  sufficient  guarantee 
against  the  chances  of  accident ;  and,  besides,  we  may,  by  increasing 
a  little  the  mean  expense,  increase  the  number  to  four  under  some 
circumstances,  as  an  exception  to  the  general  rule. 

THIRD.  That  the  repairs  of  the  implements  under  discussion  may  be 
easily  made  by  all  the  clock  or  watchmakers,  or  other  mechanicians, 
to  whom  we  have  recourse  for  repairing  the  revolving  machinery  of 
light-houses. 

I  conclude  with  the  remark  that,  if  it  be  determined  to  multiply 
the  application  of  the  new  system  of  maritime  illumination  in  the 
United  States,  it  seems  to  me  that  it  will  be  expedient  to  engage  one 
of  the  foremen  employed  in  the  manufactory  of  our  mechanical  lamps  to 
go  to,  and  remain  in  the  country  for  several  years.  By  that  measure, 
which  would  be  attended  with  very  little  expense,  all  the  difficulties 
which  might  presnet  themselves  at  first  in  establishing  lenticular 
lights  would  be  removed,  and  the  perfect  regularity  of  the  service 
of  these  new  establishments  would  be  insured. 

LEONOR  FRESNEL. 

PARIS,  December  31,  1845. 


PAPER  ON  FRENCH   LIGHTS  ACCOMPANYING   REPORT  OF  THE   LIGHT-HOUSE 
BOARD  OF  THE  UNITED  STATES. 


[REPORT  or  Lieuts.  THORNTON  A.  JENKINS  and  RICHARD  BACHE,  U.  S.  Navy,  to  the  Secretary 
of  the  Treasury,  June  22,  1846.— Senate  Doc.,  1st  session  29th  Congress,  No.  488,  p.  70.] 


The  Light-house  Department  of  France  is  attached  to  the  official 
duties  of  the  minister,  Secretary  of  State  for  the  Interior,  and  is 
under  the  immediate  control  and  direction  of  the  Minister  of  Public 
Works,  charged  with  the  administration  of  the  bridges  and  roads. 

A  central  public  board  has  the  management  of  all  light-houses, 
buoys,  beacons,  and  sea-marks  on  the  coasts,  which  is  composed  of 
eleven  distinguished  scientific  and  professional  individuals,  who  are 
appointed  by  the  government,  including  the  engineer,  secretary  to 
the  commission,  and  his  assistant.  This  board  is  presided  over  by 
the  Minister  of  Public  Works,  and  in  his  absence  by  the  Under  Sec- 
retary of  State  for  that  department. 

This  mixed  commission,  called  the  "Commission  des  Phares,"  is 
composed  of  naval  officers,  (of  whom  there  is  a  majority,)  of  inspectors 
of  the  corps  of  bridges  and  roads,  and  of  members  of  the  institute. 
It  prepares  the  projets  for  all  new  lights,  and  the  general  council  of 
bridges  and  roads  judges  of  the  propriety  of  all  schemes  for  that 
branch  of  service,  under  the  four  heads  of  Architectural  Design, 
Mode  of  executing  the  Works,  Estimate  -of  the  Expense,  and  the 
Preparation  of  the  Specifications  of  the  Works.  The  light-house 
commission  of  France  is  not  an  administrative  body,  but  is  occupied 
solely  in  questions  of  principle  or  design,  and  leaves  to  the  general 
directory  of  bridges  and  roads  the  care  of  providing  the  necessary 
means  for  the  construction  of  new  works,  the  expenses  of  illumina- 
tion, <fec. 

The  central  commission  at  Paris  is  charged  with  the  duty  of  pro- 
viding all  supplies  necessary  for  keeping  the  illuminating  apparatus 
in  perfect  order.  There  is  also  in  Paris,  belonging  to  this  particular 
branch  of  the  public  service,  a  central  workshop  and  depot,  under 
the  immediate  care  and  supervision  of  the  secretary-engineer  to  the 
commission,  who  superintends  the  construction  (by  mechanics  em- 
ployed by  the  administration)  of  all  lanterns  and  their  fixtures  that 


7 

may  be  required  for  the  service  ;  tests  all  apparatus  before  sending 
it  to  its  destination  ;  makes  experiments  upon  all  the  optical  and 
mechanical  portions  of  apparatus  destined  for  light-house  purposes, 
combustibles,  &c. ;  in  short,  this  officer  is  charged  with  all  the  scien- 
tific details  of  the  service,  subject  to  the  instructions,  from  time  to 
time,  which  may  be  issued  by  the  light-house  commission.  At  this 
central  depot  are  always  kept,  ready  for  immediate  use,  the  various 
articles  required  in  the  illuminating  department ;  such,  for  example, 
as  mechanical  and  Argand  lamps,  glass  chimneys,  wicks,  cleaning 
materials,  £c. ;  also  specimens  of  the  different  descriptions  of  appa- 
ratus used  in  light-houses,  and  apparatus  constructed  upon  the  latest 
and  most  approved  plans  ready  for  service. 

All  expenses  incurred  in  the  maintenance  of  the  lights  and  their 
appendages  are  defrayed  by  the  agents  of  the  national  treasury, 
from  funds  authorized  by  annual  appropriations  for  those  specific 
purposes. 

No  light  dues  are  charged  upon  shipping  in  France,  as  in  Great 
Britain,  Holland,  Denmark,  Norway,  and  Sweden,  <fcc.  ;  but  the 
whole  establishment  is  provided  for  as  in  the  United  States  and 
Russia. 

The  maintenance  of  the  light-house  buildings  is  confided  to  the 
departmental  or  local  engineers,  and  the  expenses  are  defrayed  from 
funds  appropriated  for  the  service  of  the  department  of  public  works. 

The  establishment  of  new  works  is  decided  upon  by  the  Minister 
of  Public  Works,  under  the  advice  of  the  light-house  commission. 
The  determination  of  the  minister  is  reported  officially  by  the  secre- 
tary of  the  commission  to  the  Under  Secretary  of  State  for  that 
department,  and  through  his  office  to  the  Prefect  of  the  department 
in  which  the  proposed  work  is  to  be  established.  The  Prefect  directs 
the  chief  engineer  of  bridges  and  roads  for  that  department  to  have 
detailed  plans  and  estimates  prepared  upon  the  basis  of  the  proposi- 
tion of  the  light-house  commission  5  these  plans  and  estimates  are 
transmitted  through  the  office  of  the  Under  Secretary  of  State  to  the 
secretary  of  the  light-house  commission,  who  makes  a  report  to 
accompany  them  to  the  light-house  commission.  The  plans  and 
estimates  are  then  submitted  to  the  light-house  commission,  which 
decides  whether  or  not  the  wants  of  the  service,  nautically  or  other- 
wise, are  such  as  to  require  the  construction  of  the  proposed  works. 
In  the  preparation  of  these  plans  and  estimates,  the  military  engineer 
of  the  department  is  consulted,  to  ascertain  his  opinions  as  to  the 


8 

propriety  of  constructing  these  works  with  reference  to  the  defences 
of  the  coast. 

The  details  having  been  completed,  after  having  undergone  the 
strictest  scrutiny  in  every  particular,  the  projet  is  presented  to  the 
general  council  of  bridges  and  roads,  to  be  considered  with  reference 
to  the  architectural  designs,  mode  of  construction,  estimate  of  ex- 
pense, &c.  Having  been  approved  by  the  general  council  of  bridges 
and  roads,  and  the  Minister  of  the  Interior,  the  plan  is  then  sent  to 
the  Prefect  of  the  department  in  which  the  light  is  to  be  established, 
with  instructions  to  enter  into  contracts  for  the  execution  of  the 
works,  under  the  specifications  and  limitations  authorized  by  the 
administration. 

The  execution  of  these  works  is  entrusted  to  the  engineers  of 
bridges  and  roads  for  that  department.  As  the  works  advance,  the 
contractor  receives  payments  upon  the  certificates  of  the  engineers 
in  charge,  approved  by  the  Prefect  of  the  department,  from  the 
departmental  paymaster,  (as  deputy  of  the  public  treasury,)  and  the 
sums  are  charged  to  the  budget  for  works  of  navigation,  under  the 
head  of  light-houses. 

The  light-house  towers  of  France  are  constructed  in  the  most  sub- 
stantial and  perfect  manner  possible,  without  there  being  any  appear- 
ance of  unnecessary  or  wasteful  expenditure.  Great  care  is  taken 
in  the  interior  arrangements  of  the  buildings,  so  that  they  may  best 
answer  the  requirements  of  the  service.  Many  of  the  towers  are 
constructed  of  a  soft  stone  of  a  rather  peculiar  kind,  which  hardens 
by  exposure  to  the  action  of  the  atmosphere  :  those  constructed  of 
that  material  are  lined  inside  with  brick,  leaving  a  sufficient  space 
between  the  interior  of  the  outer  wall  and  the  brick  to  allow  a  free 
circulation  of  air,  thereby  securing  the  building  from  dampness. 
Hard  burnt  bricks  are  preferred  for  light-house  towers,  when  circum- 
stances will  admit  of  their  being  employed,  particularly  in  fitting  up 
the  oil  apartments,  which  are  placed  below  the  surface  of  the  earth, 
to  insure  as  equable  a  temperature  during  the  whole  year  as  may  be 
possible  to  attain.  The  keepers'  apartments  are  finished  and  fitted 
up  in  a  plain,  substantial  and  economical  manner,  combining  all  the 
necessary  accommodation  and  comfort.  There  is  a  room  fitted  and 
properly  furnished  for  the  accommodation  of  the  engineer,  inspector, 
or  other  person  authorized  to  make  official  visits,  at  each  light-station. 
Especial  care  is  taken  to  secure  proper  ventilation  to  the  towers  and 
lanterns — all  the  necessary  fixtures  about  the  light-rooms,  lanterns, 


9  m "! 

apparatus,  &c. — the  most  minute,  and  apparently  unimportant  details 
in  the  exterior  and  interior  arrangements  ;  in  short,  nothing  could 
combine  greater  perfection  in  stability,  in  usefulness,  and  a  proper 
economy,  than  is  perceptible  in  everything  connected  with  the  light- 
houses visited  by  us  on  the  coasts  of  France. 

The  repairs  of  the  light-houses  and  their  appendages  are  projected 
and  executed  \)y  the  engineers  of  the  different  departments  in  which 
they  exist,  who  are  limited  as  much  as  possible  in  their  expenditures 
by  the  estimates  of  each  year  for  those  specific  purposes.  In  some 
cases  the  contractor  general  is  authorized  to  make  repairs,  under  the 
direction  of  the  agents  of  the  administration  of  bridges  and  roads. 

Whenever  application  is  made  for  a  new  harbor  light,  the  subject 
is  submitted  to  a  local  commission,  assisted  by  the  engineers  of  the 
department.  The  report  is  discussed  by  the  light-house  commission, 
and  the  same  course  subsequently  followed  as  in  the  case  of  large  or 
seacoast  lights. 

All  the  light-house  towers  in  France  are  furnished  with  lightning- 
conductors,  made  of  copper  wire  twisted  in  the  form  of  a  rope,  and 
about  three-fourths  of  an  inch  in  diameter. 

In  the  organization  of  the  lighting  service,  two  systems  are  fol- 
lowed :  the  contract,  and  the  administrative.  The  Ocean  and  Medi- 
terannean  coasts  are  under  contract  at  present  for  nine  years  from 
1839,  for  all  the  detail  supplies  of  the  service. 

Among  the  clauses  and  conditions,  it  will  be  perceived 
that  the  contractor  general  is  required  to  be  represented  by  a  deputy 
in  each  department  in  which  there  are  any  lights  ;  that  the  oil  of 
colza,  clarified  and  refined,  must  be  used  exclusively ;  and  that  the 
prices  of  oil  will  be  regulated  quarterly,  based  upon  the  average 
prices  of  the  principal  market  in  the  kingdom  for  that  particular 
article  of  commerce.  M.  Fresnel  insists  that  this  last  clause  has  had 
a  most  salutary  effect  of  insuring  the  best  oil  the  market  could  pro- 
duce, without  the  contractor  running  any  risk  of  loss.  On  the  coast 
of  the  channel,  from  the  frontier  of  Belgium  to  St.  Malo,  this  service 
is  performed  by  the  administration,  except  for  the  article  of  oil, 
which  is  procured  under  a, contract  entered  into  for  three  years. 
That  portion  of  the  coasts  of  France  which  is  lighted  by  contract 
includes  even  the  salaries  of  the  light-keepers  ;  but  where  the  service 
is  performed  by  the  administration,  the  keepers  are  appointed  by 
the  Prefect  of  the  department,  upon  the  recommendation  of  the 
engineers.  The  smaller  articles  necessary  to  the  illumination  are 


*  10 

sent  from  the  central  depot  in  Paris,  under  the  charge  of  a  conduct- 
ing steward.  The  mechanical  lamps  are  sent  to  Paris  to  be  repaired 
under  the  engineer  secretary  to  the  light-house  commission.  The 
administrative  system  recommends  itself,  for  the  reason  that  it  avoids 
all  intervention  of  interest  foreign  to  that  for  which  the  lights  were 
established.  The  contract  system  has  been  for  a  long  time  preferred 
in  France,  for  reasons  of  economy,  complication  of  accounts  when 
performed  by  the  administration,  &c. ;  but  the  experience  of  the  last 
seven  years  on  the  channel  coast  has  sufficiently  demonstrated  the 
importance  of  changing  it  to  the  administrative  ;  and  it  is  deemed 
quite  probable,  that,  after  the  expiration  of  the  present  leases,  that 
system  will  be  exclusively  adopted,  except  for  supplies  of  oil. 

The  superintendence  of  the  lights  of  France  is  confided  to  the  local 
engineers  of  the  corps  of-  bridges  and  roads.  The  secretary  to  the 
light-house  commission  visits,  each  year,  one  of  the  three  divisions 
into  which  the  coast  is  divided,  and  his  assistant  another,  so  that  the 
inspections,  as  fur  as  possible,  are  biennial  for  each  division. 
Monthly  returns  are  made  of  all  stores  on  hand,  of  the  quantity  of 
oil  consumed  each  night,  <fcc.,  to  the  secretary  of  the  commission. 
These  returns  are  intended  as  checks  upon  the  keepers  and  answer 
the  purpose  admirably.  A  most  rigid  supervision  is  required  at  the 
hands  of  the  inspecting  engineers  ;  and,  moreover,  that  they  employ 
all  possible  means  to  detect  any  delinquency  on  the  part  of  the 
keepers,  or  other  agents  connected  with  the  service.  It  is  conceded 
that  all  these  precautions  may  foil  to  produce  the  desired  effect,  but 
that  under  such  a  supervision  few  among  the  guilty  will  escape  de- 
tection. The  lights  visited  by  the  undersigned  were  clean,  and 
presented  every  indication  of  a  perfect  and  systematic  attendance 
and  supervision. 

Indications  of  the  range  of  visibility  afford  very  meagre  data  for 
forming  a  correct  idea  as  to  the  relative  value  of  apparatus  for  illu- 
mination. It  is  impossible  to  determine  with  certainty  the  absolute 
range  of  any  light,  in  consequence  of  the  different  conditions  of  the 
atmosphere,  and  of  the  capacities  of  the  different  observers.  A  first 
order  dioptric  light  has  been  seen  fifty  miles  very  often,  and  one  of 
the  fourth  order  as  far  as  sixteen  miles.  M.  Fresnel  says  upon  the 
subject  of  range:  "We  would,  then,  draw  very  erroneous  conclu- 
sions as  to  the  relative  value  of  the  useful  effect  of  the  apparatus  of 
these  lights,  in  taking  for  a  basis  of  comparison  the  indications  of 
range,  which  are  never  fixed  or  positive." 


11 

At  the  present  time  there  are  two  systems  of  illumination  in  France 
— the  old  or  reflector  system,  and  the  new  or  dioptric  system.  In 
1822  M.  A.  Fresnel  placed  the  first  dioptric  apparatus  ever  success- 
fully employed  in  the  tower  of  Cordouan,  at  the  mouth  of  the 
Gironde.  In  1825  the  light-house  commission  decided  upon  the 
exclusive  use  of  the  lenticular  apparatus  for  the  illuminations  of  the 
coasts  of  France  and  colonies ;  adopting,  at  the  same  time,  the  pro- 
gramme and  report  of  Rear  Admiral  de  Rossel,  who  had  been  charged, 
as  a  member  of  the  "  Commission  des  Phares,"  with  that  service. 

Since  that  period  new  lights  have  been  established,  and  old  ones 
replaced  with  this  new  apparatus,  until,  on  the  31st  December,  1845, 
there  were,  of  the  two  hundred  and  nine  lights  of  every  description 
belonging  to  the  light-house  department  of  France,  one  hundred  and 
nineteen  fitted  with  that  apparatus.  The  remaining  ninety  lights 
were  reflector  lights,  fitted  with  the  Bordier  Marcet  (called  "sideral") 
reflectors,  and  the  parabolic  reflectors,  similar  to  those  used  in  Great 
Britain  and  America.  Of  these  last  ninety  lights,  seventy-seven  are 
small  harbor  or  temporary  lights,  fitted  in  most  cases  with  a  single 
parabolic  or  Bordier  Marcet  reflector,  marking  the  entrance  to  some 
channel  or  harbor.  The  remaining  thirteen  are  fitted  with  lenticular 
'apparatus  of  the  most  approved  construction,  in  accordance  with  the 
original  plan  of  1825. 

Engineers  and  other  scientific  and  philanthropic  individuals,  of 
most,  if  not  of  all,  the  nations  of  the  world,  have  made  this  new 
system  of  illumination  an  object  of  study  and  of  critical  examination  ; 
the  results  of  which  have  been  the  successful,  though  gradual,  appli- 
cation of  it  to  the  coasts  of  nearly  all  the  commercial  nations. 

On  the  31st  December,  1845,  eighty -three  light-houses  belonging  to 
foreign  governments  had  been  fitted  with  lenticular  apparatus,  con- 
structed in  Paris  ;  to  which  may  be  added  those  constructed  in 
England  and  Holland,  say  from  fifteen  to  twenty,  making,  including 
those  on  the  coasts  of  France,  upwards  of  two  hundred  and  ten ;  one 
hundred  of  which  may  be  put  down  as  of  the  three  first  orders,  and 
the  remaining  one  hundred  and  ten  of  the  fourth  order.  These 
numbers  do  not  include  those  at  present  in  the  course  of  construction 
for  France,  Egypt,  (tower  at  Alexandria,)  Brazil,  and  the  colonies, 
islands  in  the  Pacific,  &c.  M.  Fresnel  says,  with  perfect  truth  and 
reason,  "After  these  numerous  and  extended  applications,  the 
dioptric  system  of  lights  may  be  fully  appreciated  under  the  double 
aspect  of  theory  and  practice:  and  I  will  add.  that  under  the  first 


12 

point  of  view  the   question  has  been  for  a  long  time  out  of  con- 
troversy." 

There  are  six  different  orders  of  lenticular  apparatus  at  present 
employed,  viz  :  first,  second,  third  larger  model,  third  smaller  model, 
fourth  larger  model,  and  fourth  smaller  model  order. 

The  different  orders  are  subjected  to  different  combinations1,  such 
as  dioptric,  two  catadioptric,  one  with  concave  mirrors,  and  the  other 
with  catadioptric  zones,  or  rings  of  glass,  in  triangular  profile  sections, 
and  the  "diacatoptric,"  *  combining  the  dioptric  portion  and  the 
catadioptric  zones  surmounted  by  plane  mirrors.  In  addition,  a 
spherically  curved  metallic  reflector  or  mirror  is  placed  on  the  land 
side  of  all  lights  which  are  only  required  to  illuminate  from  four-fifths 
to  five-sixths  of  the  horizon,  which  reflects  the  rays  from  that  side 
back  through  the  opposite  lenses. 

"There  can  be  no  doubt,"  says  a  distinguished  engineer, t  who 
has  had  much  to  do  with  the  light-houses  of  Europe,  ' '  that  the  more 
fully  the  system  of  Fresnel  is  understood,  the  more  certainly  will  it 
take  the  place  of  all  other  systems  of  illumination  for  light-houses,  at 
least  in  those  countries  where  this  important  branch  of  administra- 
tion is  conducted  with  the  care  and  solicitude  which  it  deserves." 
"  To  the  Dutch  belongs  the  honor  of  having  first  employed  the  system 
of  Fresnel  in  their  lights."  "The  commissioners  of  northern  lights 
followed  in  the  train  of  improvements,  and  in  1834  sent  Mr.  Alan 
Stevenson  on  a  mission  to  Paris,  with  full  powers  to  take  such  steps 
for  acquiring  a  perfect  knowledge  of  the  dioptric  system,  and  for 
forming  an  opinion  of  its  merits,  as  he  should  find  necessary." 
"The  singular  liberality  with  which  he  was  received  by  M.  Leonor 
Fresnel,  brother  to  the  late  illustrious  inventor  of  the  system,  and 
his  successor  as  secretary  to  the  light-house  commission  of  France, 
afforded  Mr.  A.  Stevenson  the  means  of  acquiring  such  information 
and  making  such  a  report,  on  his  return,  as  to  induce  the  com- 
missioners of  northern  lights  to  authorize  him  to  remove  the  reflect- 
ing apparatus  of  the  revolving  light  at  InchkeitB,  and  substitute 
dioptric  instruments  in  its  place." 

"The    Trinity    House    followed    next    in    adopting    the   improved 
system."  *         Other  countries  begin  to 

show  symptoms  of  interest  in  this  important  change  ;  and  America, 
it  is  believed,  is  likely  soon  to  adopt  active  measures  for  the  im- 

6  See  Mr.  Alan  Stevenson's  Report  to  Commissioners  of  Northern  Lights  for  this  word, 
f  Mr.  Alan  Stevenson,  civil  engineer. 


13 

provement  of  their  light-houses.  "Fresnel,  who  is  already  classed 
with  the  greatest  of  those  inventive  minds  which  extend  the 
boundaries  of  human  knowledge,  will  thus,  at  the  same  time,  receive 
a  place  amongst  those  benefactors  of  the  species  who  have  conse- 
crated their  genius  to  the  common  good  of  mankind  ;  and  wherever 
maritime  intercourse  prevails,  the  solid  advantages  which  his  labors 
have  procured  will  be  felt  and  acknowledged." 

The  fourth  order  lenticular  lights  are  illuminated  ordinarily  by 
means  of  a  common  fountain,  or  constant  level  lamp  and  Argand 
burner,  with  a  single  cylindrical  wick  of  three-fourths  to  seven-eighths 
of  an  inch  in  diameter,  consuming  about  one  and  a  quarter  ounce  of 
oil  per  hour,  and  forty-eight  gallons  per  annum.  The  larger  lights 
require  mechanical  lamps  with  multiple  wicks,  to  as  great  a  number 
as  four,  placed  in  concentric  tubes,  and  the  oil  supplied  to  them  by 
means  of  pumps,  put  in  play  by  clock  machinery.  Hydraulic  and 
pneumatic  lamps  have  been  employed  in  the  place  of  the  mechanical 
ones,  but,  with  good  reason,  they  are  not  approved  of  in  France. 
For  the  catrdioptric  apparatus  of  half  a  metre  in  diameter,  the 
ordinary  constant  level  lamps,  with  two  concentric  wicks,  burning 
about  four  and  a  half  ounces  of  oil  per  hour,  have  been  employed 
very  successfully  at  several  points  on  the  coast  of  France,  where  the 
ordinary  range  of  a  light  of  the  third  order,  for  example,  was  not 
required,  or  for  harbor  lights  requiring  a  powerful  ray,  or  one  whose 
brilliancy  it  is  necessary  to  weaken  by  the  Application  of  a  red 
chimney,  with  the  view  to  give  it  a  distinctive  character.  These 
double  wick  ordinary  lamps  require  only  one  keeper  to  attend  to 
them.  Some  of  the  burners  in  France  are  fitted  with  flat  wicks  for 
small  and  temporary  lights,  although  by  no  means  common,  and 
generally  disapproved  of. 

The  dioptric  lights  of  France  are  divided  into  six  different  orders  j 
but,  with  reference  to  their  distinctive  characteristics  and  appear- 
ances, this  division  does  not  apply,  inasmuch  as,  in  every  order  or 
class,  lights  of  precisely  the  same  character  may  be  found,  differing 
only  in  the  distance  at  which  they  can  be  seen,  and  in  the  expense 
of  their  maintenance.*"  The  six  different  orders,  as  before  mentioned, 
are  not  intended  as  distinctions,  ' '  but  are  characteristic  of  the  power 
and  range  of  lights,  which  render  them  suitable  for  different  localities 
on  the  coasts,  according  to  the  distance  at  which  they  can  be  seen." 
''This  division,  therefore,  is  analogous  to  that  which  separates  the 
lights  of  Great  Britain  into  sea  lights,  secondary  lights,  and  harbor 


14 

lights,  terms  which  are  used  to  designate  the  power  and  position, 
and  not  the  appearance  of  the  lights  to  which  they  are  applied." 

In  France  there  are  nine  principal  combinations  of  lights  possessing 
distinctive  characteristics.  These  distinctions,  for  the  most  part, 
depend  upon  the  periods  of  revolution  rather  than  upon  the 
characteristic  appearance  of  the  light.  They  are — 

1.  Flashes,  which  succeed  each  other  every  minute. 

2.  Flashes,  which  succeed  each  other  every  half-minute. 

3.  Flashes,  alternately  red  and  white. 

4.  Fixed  lights,  varied  by  flashes  every  four  minutes. 

5.  Fixed  lights,  varied  by  flashes  every  three  minutes. 

6.  Fixed  lights,  varied  by  flashes  every  two  minutes. 

7.  Fixed  white  lights,  varied  by  red  flashes  more  or  less  frequent. 

8.  Fixed  lights. 

9.  Double  fixed  lights. 

There  are  very  few  double  fixed  lights  in  France.  They  are, 
however,  sometimes  employed  for  the  purpose  of  giving  a  very 
decided  character  to  the  locality.  For  example,  the  first  order  lights 
at  La  Heve,  near  the  port  of  Havre,  and  the  two  lights  at  present  in 
the  course  of  construction  on  the  left  bank  of  the  Canche.  Red  fixed 
lights  are  not  employed  on  the  coasts  of  France,  except  as  a 
distinguishing  characteristic  for  harbor  purposes.  They  are  doubly 
objectionable  ;  first,  because  of  the  great  diminution  of  light  in 
consequence  of  the«  absorption  of  the  red  glass  chimney  ;  and, 
secondly,  it  loses  its  distinctive  character  in  foggy  weather,  all  lights 
assuming  a  reddish  tint  under  those  circumstances. 

The  revolving  reflector  lights  are  objected  to  because  of  the  fact 
that,  ordinarily,  they  are  only  distinguishable  by  the  duration  of  their 
eclipses,  which  often  become  positive  at  a  very  short  distance  from 
the  light-house,  and  the  interval  of  time  between  any  two  eclipses 
could  not  be  extended  to  a  greater  limit  that  three  minutes  without 
prolonging  the  duration  of  the  eclipses  to  such  an.extent  of  time  as 
to  mislead  the  navigator  by  depriving  him  for  so  long  a  time  of  his 
point  of  recognition.  In  the  revolving  dioptric  apparatus,  upon  the 
latest  and  most  approved  plan,  the  duration  of  the  eclipses  is  scarcely 
perceptible,  the  fixed  subsidiary  parts  of  which  reflect  a  light  con- 
stantly visible  in  a  horizon  extending  nine  or  ten  nautical  miles  with 
a  second  order,  and  from  twelve  to  fifteen  with  a  first  order 
apparatus. 

The  three  first  of  the  principal  combinations  only  are  applied  to 


15 

the  first  three  orders,  in  consideration  that  in  the  inferior  orders  the 
flashes  would  have  too  short  a  duration,  and  the  eclipses  would  be 
positive  at  too  short  a  distance  from  the  light,  in  consequence  of  the 
feebleness  of  the  ray  produced  by  the  fixed  subsidiary  part  of  the 
apparatus. 

The  distinguished  engineer,  secretary  to  the  "Commission  des 
Phares"  of  France,  M.  Leonor  Fresnel,  kindly  furnished  the  under- 
signed with  the  results  of  numerous  photometric  experiments  which 
were  made  for  the  purpose  of  testing  the  comparative  useful  and 
economical  effects  of  the  two  systems  of  illumination,  to  which  they 
beg  leave  to  call  particular  attention. 

M.  Fresnel  says,  in  his  note  referred  to,  ' '  the  foregoing  results 
confirm  the  following  principles  : 

"1.  The  useful  effect  of  a  parabolic  reflector  increases  with  its 
dimensions,  and  with  that  of  the  illuminating  body. 

' '  2.  The  economical  effect  of  a  reflector  of  given  dimensions  is 
greatest  when  the  lamp-burner  is  smallest. 

' '  The  divergence  is  greatest  when  the  flame  is  most  voluminous,  or 
when  the  reflector  is  smallest.  We  cannot  then  (all  other  things 
being  equal)  augment  the  economical  effect  of  a  reflector  without 
diminishing  its  useful  effect ;  that  is  to  say,  without  reducing  its 
brilliancy  or  intensity,  and  consequently  its  range  (portee). 

"The  reduction  of  the  volume  of  light  within  certain  limits  is 
particularly  objectionable  when  it  appertains  to  eclipse  apparatus,  in 
which  case  it  limits  the  width  of  the  luminous  cone,  and  consequently 
augments  the  length  of  the  eclipses.  The  same  reduction  applied  to 
the  foci  of  reflectors  composing  a  fixed  light  apparatus  may  weaken 
the  light  in  their  intervals  to  such  a  degree  as  to  produce  dead  angles, 
or  become  completely  obscured  to  the  observer  beyond  certain  dis- 
tances. 

"  It  is  further  proper  to  remark  that  the  horizontal  divergence  is 
not  lost  for  useful  effect,  but  that  the  divergence  in  the  vertical  sense 
only  profits  the  navigator  in  the  limited  angular  space  comprised 
between  the  tangent  at  the  surface  of  the  sea  and  the  ray  terminating 
at  the  distance  of  some  miles  from  the  light. 

1 '  Finally,  there  is  for  the  calibre  of  the  lamp  burners  applicable 
to  reflectors  of  given  dimensions,  and  destined  for  the  illumination 
of  an  equally  determined  range,  a  maximum  beyond  which  prodigality 
of  light  ensues,  and  a  minimum  within  which  the  illumination 
becomes  insufficient.'' 


16 

The  third  order  smaller  size  lenticular  apparatus  may  be  illumi- 
nated with  very  decided  advantages  by  means  of  an  ordinary  Argand 
burner  and  single  wick.  Such  a  light  would  consume  about  two 
ounces  of  oil  per  hour,  and  is  admirably  adapted  for  harbor  lights. 
In  ordinary  weather  such  a  light  may  be  seen  from  twelve  to  fifteen 
miles.  One  keeper  alone  can  attend  to  all  the  duties  of  such  a  light, 
and  it  is  maintained  in  France  at  an  annual  expense  of  about  two 
hundred  dollars. 

M.  Fresnel  remarks,  with  reference  to  the  ranges  of  different 
lights,  their  useful  effect,  <fec.  : 

"The  useful  effect  of  a  light-house  apparatus  is  measured  by  the 
quantity  of  light  which  it  projects  upon  the  horizon.  Observations 
of  range  for  that  purpose  furnish  very  uncertain  evidences,  on  account 
of  the  difficulty  of  ascertaining  the  absolute  range  of  a  light,  which 
varies  according  to  the  state  of  the  atmosphere  and  according  to  the 
good  or  bad  sight  of  the  observers." 

Reflector  lights,  with  not  more  than  six  or  eight  burners,  are 
attended  by  one  keeper,  occasionally  assisted  by  the  members  of  his 
family.  For  lights  with  a  larger  number  of  burners,  two  keepers  ; 
and  if  the  light  be  in  an  isolated  position,  three  keepers  are  allowed, 
with,  in  the  latter  cases,  certain  privileges  not  accorded  to  others. 

Dioptric  lights  of  the  fourth  order  and  third  order  smaller  size, 
require  but  one  keeper,  except  when  in  isolated  positions.  Two 
keepers  are  allowed  to  lights  of  the  third  order  larger  size,  and  for 
those  of  the  second  order,  in  consequence  of  the  employment  of  the 
mechanical  lamp. 

First  order  lights  are  allowed  three  keepers  ;  and  when  there  are 
two  first  order  lights  forming  one  combination,  five  keepers  are 
allowed  for  the  two  lights.  Lights  of  the  first  order  in  isolated 
positions,  are  allowed  four- keepers,  and  for  the  third  order  larger 
size  and  the  second  order  lights,  similarity  situated,  three  keepers 
are  allowed.* 

In  comparing  the  two  systems  of  illumination,  they  should  be  con- 
sidered under  the  heads — first,  of  absolute,  useful,  and  economical 
effect ;  second,  of  first  cost,  repairs,  and  maintenance  ;  and,  thirdr 
of  the  facility  and  safety  of  the  service. 

The  brilliancy  of  a  catadioptric  apparatus  of  11-8  inches  in  di- 
ameter, lighted  by  a  lamp  burning  forty-five  grammes  of  oil  per  hour, 

°In  England,  Scotland,  and  Ireland,  no  difference  is  made  between  the  number  of 
keepers  for  dioptric  and  reflector  lights. 


17 

has  been  found,  by  photometric  experiments,  to  be  equal  to  eight  or 
nine  Carcel  burners;  while  that  of  a  "sideral"  reflector  of  Bordier 
Marcet,  illuminated  by  a  lamp  consuming  fifty  grammes  of  oil  per 
hour,  has  been  found,  in  the  same  manner,  equal  to  only  four  burners 
of  Carcel;  or  in  other  words,  the  brilliancy  of  the  former  is  to  the 
latter  as  one  to  two.  The  useful  effect  of  the  catadioptric  apparatus, 
illuminating  three-fourths  of  the  horizon,  is  represented  by  137,700, 
and  that  of  the  reflector  by  68,400,  which  gives  the  value  as  one  to 
two. 

The  economical  effect  of  the  catadioptric  apparatus  is  represented 
by  3060?  and  that  of  the  reflector  by  1368;  giving  the  value  in  that 
respect  as  1  to  2  •  24. 

No  combination  of  reflectors  can  produce  an  equivalent  to  the  third 
order  smaller  size  apparatus,  illuminated  by  an  ordinary  fountain 
lamp  and  Argand  burner,  with  one  wick,  consuming  sixty  grammes 
of  oil  per  hour,  or  one  burner,  with  two  wicks,  consuming  one 
hundred  and  fifteen  grammes  of  oil  per  hour.  An  apparatus  of  this 
sort,  with  a  lamp  of  two  wicks,  may  be  seen  in  ordinary  weather  (the 
horizon  of  the  light,  from  its  elevation  above  the  sea  level,  being 
equal  to  or  greater  than  that  distance)  at  the  distance  of  fifteen  to 
eighteen  nautical  miles. 

The  brilliancy  of  a  catadioptric  third  order  larger  size  apparatus, 
illuminated  by  a  mechanical  lamp  of  two  wicks,  consuming  one  hun- 
dred and  ninety  grammes  of  oil  per  hour  (six  and  three-fourth 
ounces.)  has  been  found  equal  to  seventy  burners. 

We  suppose  that  it  embraces  only  four-fifths  of  the  horizon.  To 
illuminate,  by  means  of  reflectors,  the  same  angular  space  of  288°, 
with  an  effect  of  light  about  equal,  fourteen-  parabolic  reflectors,  of 
about  eleven  inches  in  diameter,  illuminated  by  Argand  lamps,  con- 
suming each  thirty-five  grammes  of  oil  per  hour,  will  be  required. 
The  useful  effect  of  these  reflectors  will  be  represented  by  870,240, 
and  that  of  the  catadioptric  apparatus  by  1,160,000;  and  thus  it  is 
seen,  that  notwithstanding  the  very  great  difference  in  favor  of  the 
catadioptric  apparatus,  in  the  consumption  of  oil,  it  is  also  superior 
in  useful  effect  to  the  light  with  the  fourteen  parabolic  reflectors. 
Further,  the  economical  effect  of  the  catadioptric  apparatus  is  repre- 
sented by  6105,  and  that  of  the  reflector  by  1776,  or  as  1  to  3-44  : 
''that  is  to  say,  without  estimating  the  expenditure  of  oil  by  unity  of 
light,  the  lenticular  light  will  be  nearly  three  and  half  times  more 
advantageous  than  the  reflector  light."  With  regard  to  the  effective 
2 


18 

expenditure  of  oil,  they  will  be  in  the  proportion  of  190  grammes  to 
14  X  35  grammes  per  hour,  or  as  1  to  2.6. 

The  brilliancy  of  a  catadioptric  apparatus  of  the  second  order, 
with  a  mechanical  lamp  of  three  concentric  wicks,  consuming  500 
grammes  of  oil  per  hour,  has  been  found  equal  to  264  burners. 
Supposing  that  it  is  only  required  to  illuminate  three-fourths  of  the 
horizon,  then,  to  obtain  an  effect  about  equal  in  angular  space  of  270°, 
at  least  34  parabolic  reflectors  of  about  20  inches  in  diameter  will  be 
required,  which  will  give  a  useful  effect  which  is  represented  by 
3,525,120,  while  that  of  the  catadioptric  apparatus  is  represented  by 
4,120,000.  The  comparison  between  the  absolute  consumption  of 
oil  will  be  equal  to  2-86  to  1,  and  that  of  the  quantity  of  oil  expended 
by  unity  of  light  equal  to  3 '33  to  1 ;  thus,  under  this  last  report,  the 
lenticular  apparatus  will  be  three  and  a  third  times  as  advantageous 
as  the  catoptric  apparatus. 

The  maximum  brilliancy  of  a  revolving  light  of  the  second  order, 
with  12  lenses,  has  been  found  to  be  equal  to  1,184  burners,  and  its 
minimum  brilliancy  equal  to  104  burners.  To  construct  a  light,  with 
parabolic  reflectors,  possessing  an  equal  effect,  it  will  require  24 
with  diameters  from  22  inches  to  24  inches,  arranged  on  six  faces  of 
the  revolving  frame.  In  making  the  comparison,  however,  for  want 
of  precise  data  as  to  the  lustres  of  those  reflectors,  those  of  about 
20  inches  diameter  will  be  referred  to.  It  is  supposed  that  the  two 
lights  compared  are  constructed  so  as  to  present  the  same  distin- 
guishing features;  the  maximum  lustre  of  the  reflector  light  will  be 
equal  only  to  1,080  burners,  with  other  disadvantages,  for  the  details 
of  which  reference  may  be  made  to  M.  Fresnel's  note  No.  1,  section 
2,  (hereto  annexed.)  M-.  Fresnel  remarks,  in  this  connection,  "with- 
out pressing  further  the  comparison  of  the  effects  of  the  two  kinds 
of  apparatus,  we  will  perceive,  without  doubt,  the  evident  advantages 
of  the  dioptric  or  lenticular  combination,  which  in  fine  weather  will 
not  present  an  absolute  eclipse  at  a  less  distance  than  from  15  to  18 
nautical  miles.  If  we  now  consider  the  expenditures  of  oil,  we  will 
find,  first,  that  they  are  as  24  X  42  is  to  500,  or  as  1  to  2  ;  second, 
that  the  economical  effects  will  be  as  2,469  is  to  10,043,  or  as  1  to 
4 '07;  thus  the  lenticular  apparatus  will  be  four  times  as  advantageous 
as  the  reflector  apparatus."  Let  us  remark,  before  proceeding 
further,  that  in  employing  24  parabolic  reflectors  of  about  20  inches 
diameter  for  such  an  apparatus  we  reach  the  utmost  possible  limit, 
without  admitting  the  employment  of  lanterns  of  a  size  beyond  all 


19 

proper  bounds;  and  we  may  also  affirm  that  very  few  of  the  catoptric 
lights,  considered  as  lights  of  the  first  order,  equal  the  lenticular 
lights  of  the  same  character  of  the  second  order. 

With  reference  to  the  first  order  dioptric  lights,  M.  Fresnel 
remarks,  in  his  note :  ' '  Now  we  have  found  that  the  total  lustre  or 
brilliancy  of  an  apparatus  of  this  kind  is  equal  in  all  its  azimuths  to 
480  burners  of  Carcel.  But  it  will  be  practically  impossible  to  obtain 
a  like  effect  in  the  catoptric  system,  without  having  recourse  to 
the  employment  of  36  parabolic  reflectors  of  about  24  inches  in 
diameter."  "The  difficulty  becomes  still  greater,  if  it  be  necessary 
to  attain  with  these  reflectors  the  effect  of  a  revolving  lenticular 
light,  with  eight  large  lenses,  the  lustres  or  flashes  of  which  exceed 
4000  burners  of  the  Carcel  lamp." 

"Let  us  limit,  ourselves,  then,  without  entering  into  more  full 
details,  to  the  observation,  that  the  economical  effect  of  a  fixed  light 
of  the  first  order,  illuminating  three-fourths  of  the  horizon,  is  to  the 
economical  effect  of  a,  light  composed  of  parabolic  reflectors  of  about 
twenty  inches  diameter,  as  10,080  to  2,469  or  as  4-08  to  1:  that  is 
to  say,  that  the  first  will  be  (as  to  the  expense  of  the  oil  only)  four 
times  as  advantageous  as  the  second." 

With  regard  to  lights  varied  by  flashes  or  short  eclipse  lights,  "the 
catoptric  system  is  not  susceptible  of  producing  that  combination 
without  great  difficulty,  which  unites  to  the  permanence  of  fixed 
lights  the  advantage  of  presenting  a  very  decided  character.' '  No 
repairs  are  required  upon  the  lenticular  apparatus. 

The  amount  necessary  to  construct  and  put  into  operation  ' '  sideral " 
light  for  harbor  purposes  may  be  stated  at  8,150  francs,  or  about 
$1,500;  and  the  annual  expense  for  its  maintenance,  including 
interest  upon  the  cost  at  the  rate  of  five  per  cent.,  at  1,207  francs, 
or  about  $225. 

The  amount  necessary  for  a  catadioptric  smaller  model  harbor  light 
may  be  put  down  at  9,181  francs,  or  about  $1,700;  and  the  annual 
expense  for  maintenance,  including  interest  of  first  cost,  &c.,  as 
above,  at  1,259  francs,  or  about  $235. 

The  useful  effect  of  the  "sideral"  light  has  been  found  equal  to 
68,400,  and  its  economical  effect  represented  by  57. 

The  useful  effect  of  the  catadioptric  light,  illuminating  three- 
fourths  of  the  horizon,  has  been  found  equal  to  137,700,  and  its 
economical  effect,  after  the  same  manner,  is  represented  by  109. 
The  comparison  of  these  two  will,  then,  be  in  the  proportion  of  57 


20 

to  109,  or  as  1  to  1-91.  "Then,  besides  the  advantages  of  a  double 
lustre,  the  catadioptric  apparatus,  in  an  economical  point  of  view,  is 
nearly*  twice  as  advantageous  as  the  catoptric  apparatus." 

M.  Fresnel  remarks  :  "  It  is  difficult  to  establish  a  comparison  of  a 
precise  kind  between  the  fixed  lights  of  the  third  order  in  the  old 
and  the  new  systems,  because  we  cannot  obtain  with  the  ordinary 
parabolic  reflectors  a  passably  equal  distribution  of  light,  without 
multiplying  those  reflectors  to  such  a  number  as  would  require  a 
much  greater  expenditure  of  oil  than  could  be  allowed  for  lights  of 
that  class."  He  says  further:  "I  will  merely  observe  that  I  have 
every  reason  to  believe,  from  the  indications  contained  in  the  table 
of  light-houses  of  the  United  States,  that  among  all  the  lights  of  that 
country  illuminated  by  reflectors,  the  diameters  of  which  do  not  ex- 
ceed sixteen  English  inches,  ' '  there  are  very  few  whose  useful  effect 
is  superior  or  equal  to  that  of  a  catadioptric  light  of  the  third  order 
larger  model." 

The  amount  necessary  for  establishing  a  reflecting  revolving  light 
with  twenty-four  parabolic  reflectors  of  about  twenty  inches  diameter 
is  estimated  at  73,000  francs,  or  about  $13,700. 

Annual  expense  for  maintenance  of  the  same,  including  interest 
at  five  per  cent,  per  annum,  will  be  8,650  francs,  or  about  $1,625. 

The  amount  necessary  for  establishing  a  second  order  revolving 
lenticular  light  is  estimated  at  105,500  francs,  or  about  $19,800. 

The  annual  expense  for  maintenance  of  the  same,  including  interest 
at  five  per  cent,  per  annum,  will  be  11,075  francs,  or  about  $2,075. 

The  useful  effect  of  the  reflector  light  is  represented  by  2,488,320, 
and  its  economical  effect  by  288. 

The  useful  effect  of  the  lenticular  light  is  represented  by  5,021,467, 
and  its  economical  effect  by  453. 

The  economical  effect  of  these  two  lights  will  then  be  represented 
by  288  and  453,  or  in  the  proportion  of  1  to  1*6.  "From  whence 
it  results  definitively  that  the  lenticular  light  of  the  second  order  will 
be  more  than  one  and  a  half  times  as  advantageous  as  the  catoptric  or 
reflector  light,  which  we  may  without  doubt  consider  as  being  of  the 
first  order,  and  the  useful  effect  of  which,  nevertheless,  could  not  be 
equal  to  but  half  of  the  useful  effeci  of  the  former." 

No  comparison  can  be  entered  into  between  the  first  order  lenticular 
lights  and  reflector  lights,  for  the  reason  that  it  is  impossible  to  con- 
struct a  reflector  light  which  would  produce  a  sufficiently  powerful 
effect  to  be  compared  to  a  dioptric  one,  without  increasing  the  dimen- 


21 

sions  of  the  lantern,  and  the  number  and  size  of  the  reflectors,  to 
a  degree  which  would  be  attended  with  a  very  great  expense,  and 
equally  great  inconvenience. 

From  the  foregoing  details,  which  have  been  drawn  mainly  from 
information  furnished  by  M.  Fresnel,  the  following  seems  to  be  but 
just  conclusions: 

"1.  That  the  lights  fitted  with  the  dioptric  apparatus  present  a 
variety  in  their  power  and  effects,  and  may  be  made  to  produce  an 
intensity  of  lustre,  which  render  them  of  an  interest,  in  a  nautical 
point  of  view,  incontestably  superior  to  those  fitted  with  the  catoptric 
apparatus. 

"2.  That  if  we  take  into  account  the  first  cost  of  construction  and 
the  expense  of  their  maintenance,  we  will  find,  with  respect  to  the 
effect  produced,  the  new  system  (dioptric)  is  still  from  once  and  a  half 
to  twice,  as  advantageous  as  the  old  (reflector.)  " 

If  additional  arguments  and  evidence  were  wanting  to  establish  the 
now  almost  universally  conceded  fact,  of  the  very  positive  and  de- 
cided advantages  of  the  dioptric  system  of  Fresnel  over  all  other 
modes  of  illumination  for  light-houses,  they  might  be  found  to  exist 
at  present  in  an  unanswerable  form — that  of  the  practical  and  suc- 
cessful application  of  the  system,  within  the  last  few  years,  in  nearly 
all  the  commercial  nations  of  the  world.  Prior  to  the  year  1832, 
there  was  not  a  single  dioptric  light  out  of  France  ;  and  on  the 
French  coast,  at  as  late  a  period  as  1834,  there  were  but  14  large  and 
15  small,  or  harbor  lights,  fitted  with  the  dioptric  apparatus. 

On  the  31st  December,  1845,  there  were  belonging  to  the  French 
light-house  department  one  hundred  and  tioelve  lights  fitted  with  the 
dioptric  apparatus,  and  throughout  the  world  not  less  than  tivo  hun- 
dred and  fen  lights  fitted  upon  this  new  system  ;  one  hundred  of  which 
are  of  the  three  first  orders,  and  the  remaining  one  hundred  and  ten, 
small  or  harbor  lights,  without  including  apparatus  now  in  course  of 
construction  at  Paris,  to  which  allusion  has  already  been  made. 

The  objections  which  have  been  made  by  a  few  persons  to  the  em- 
ployment of  the  Fresnel  dioptric  apparatus  for  the  illumination  of 
light-houses,  in  consequence,  as  they  allege,  of  the  difficulties  which 
attend  the  management  of  the  mechanical  lamps  with  concentric  wicks 
(which  are  absolutely  necessary  for  the  proper  illumination  of  the 
larger  orders  of  apparatus)  seem  to  be  no  longer  tenable,  if  indeed 
there  ever  were  any  reasonable  grounds  of  objection  on  that  account. 

The  twenty-three  years'   experience  in  France  (dating  from  the. 


22 

time  the  Cordouan  light  was  exhibited,)  where  ordinary  day  laborers 
are  taken  for  light-keepers,  and  the  undeniable  fact  of  the  successful 
employment  of  the  system  for  fourteen  years  in  Holland,  Scotland, 
and  Norway;  for  from  five  to  ten  years  in  England,  Sweden,  Denmark, 
Prussia,  Belgium,  Spain,  Sardinia,  Tuscany,  Naples,  Brazils,  West 
Indies,  islands  of  the  Pacific  ocean,  Cape  of  Good  Hope,  <fcc.,  must 
be  sufficient  evidence  to  convince  any  disinterested  and  unprejudiced 
mind  of  the  utter  folly  of  such  an  objection  at  the  present  day. 

In  a  communication  to  the  government  of  Norway  and  Sweden  in 
1830,  M.  Fresnel  remarks  upon  this  subject:  "Happily,  an  experi- 
ence of  seven  years  has  dissipated  that  fear,  and  the  lenticular  lights 
have  been  distinguished  up  to  this  time  by  the  regularity  of  their 
service.''  Again,  in  reference  to  the  same  subject,  M.  Fresnel  re- 
marks, in  a  note  to  the  undersigned,  that  "opinions  thus  expressed 
fifteen  years  since,  based  upon  an  experience  of  seven  years,  have 
been  greatly  strengthened  up  to  the  present  time,  embracing  a  period 
of  twenty-two  years  since  the  establishment  of  the  Cordouan  light,  and 
sustained  by  the  results  daily  offered  of  more  than  one  hundred  and 
ten  lights  of  the  first  three  orders,  established  along  the  coasts  of 
France  and  different  foreign  powers."  "In  this  important  point  of 
view,  then,  the  question  seems  to  be  irrevocably  settled,  and  I  will 
only  add  a  few  considerations  relative  to  the  application,  more  or  less 
extended,  which  may  be  made  of  the  new  system  of  illumination  to 
the  vast  maritime  coasts  of  the  United  States." 

It  has  been  further  objected  that  competent  persons  could  not  be 
procured  in  the  United  States  to  take  charge  of  the  lights  fitted  with 
the  dioptric  apparatus  and  mechanical  lamps,  for  the  salaries  at 
present  paid  to  light-keepers  of  the  existing  lights.  The  number  of 
keepers  necessary  for  those  lights  has  also  been  urged  as  an  objection 
to  their  introduction ;  and  there  is  also  a  third  objection,  emanating 
from  the  same  source,  that  the  mechanical  lamps  could  not  be  repaired 
when  employed  at  distant  or  isolated  points  on  the  coast. 

With  regard  to  the  keepers,  no  better  evidence  can  be  adduced 
than  the  opinions  of  M.  Fresnel  upon  the  subject,  and  the  practical 
results  furnished  daily  wherever  the  lights  are  employed.  M.  Fresnel 
says,  "that  the  difficulty  of  obtaining  proper  persons  to  fill  these 
subaltern  stations  appears  to  be  most  singularly  exaggerated.  ' '  In 
France  they  belong  almost  always  to  the  class  of  ordinary  mechanics 
or  laborers,  who  make  from  one  and  half  to  two  and  half  francs  per 
day  (from  27  to  46  cents.)  "  "  Eight  or  ten  days  will  suffice  ordinarily 


23 

to  instruct  a  light-house  keeper  in  the  most  essential  parts  of  his 
duty,  receiving  lessons  from  an  instructor  conversant  with  all  the 
details  of  the  service  ;  and  two  instructing  officers  will  be  sufficient 
to  prepare  keepers  for  all  the  lenticular  lights  which  could  be  suc- 
cessively established  upon  the  coasts  of  North  America."  "In  de- 
fence of  this  assertion,  I  will  cite  the  example  of  the  administration 
of  Norway  and  Sweden." 

As  to  the  number  of  keepers  allowed  to  the  dioptric  lights,  there 
might  be  some  reason  in  the  objection,  if  it  were  possible  to  produce 
a  light  with  parabolic  reflectors  possessing  in  any  reasonable  degree 
the  advantages  arising  from  the  employment  of  a  first  order  catadi- 
optric  apparatus  ;  but  as  it  is  well  established  that  reflectors  are  not 
susceptible  (practically)  of  any  combination  which  would  produce  a 
light  equal  in  every  respect  to  a  first  order  dioptric  light,  the  objec- 
tion ought  in  honesty  to  be  abandoned  or  waived  by  them,  without 
they  prefer  bad  to  good  lights,  to  guide  the  mariner  in  his  perilous 
way  along  our  shores. 

The  lower  orders  of  dioptric  apparatus,  illuminated  by  ordinary 
Argand  lamps  and  burners,  with  single  and  double  wicks,  require 
but  one  keeper,  and  they  produce  a  light  far  superior  to  those  of  the 
same  class  in  the  catoptric  system,  independently  of  the  economy  in 
the  use  of  the  dioptric  lights.  In  Scotland  and  in  England,  where 
the  lights  are  as  well  if  not  better  attended  than  in  any  other  parts 
of  the  world,  the  same  number  of  keepers  are  allowed  for  the  same 
class  of  lights,  without  regard  to  the  apparatus  employed,  whether 
catoptric  or  dioptric.  At  the  South  Foreland,  for  example,  there  are 
only  three  keepers  for  a  first  order  dioptric  and  a  first  order  reflector 
light,  placed  about  three  hundred  yards  apart,  and  at  St.  Catherine' s 
a  first  order  dioptric  light  has  but  two  keepers  to  attend  it ;  besides, 
other  instances  might  be  cited,  if  it  were  deemed  at  all  necessary. 
But  to  accomplish  in  the  most  perfect  manner  possible  the  great  and 
important  objects  for  which  lights  are  established  upon  sea  coasts,  it 
would  seem  but  reasonable,  and  certainly  desirable,  rather  to  increase 
the  number  of  keepers  ordinarily  allowed  to  catoptric  lights  than  to 
diminish  the  number  (taking  France  as  a  basis)  for  those  fitted  with 
dioptric  apparatus. 

In  regard  to  the  repairing  of  the  mechanical  lamps,  it  may  be 
asserted,  without  the  fear  of  being  controverted,  that  in  consequence 
of  the  superior  manner  in  which  these  lamps  are  at  present  con- 
structed in  Paris,  they  will  perform  well  for  a  number  of  years  by 


24 

bestowing  upon  them  only  the  ordinary  attention  necessary  to  keep 
them  clean  ;  besides,  the  number  supplied  to  each  light-house  (from 
three  to  four,  and  never  less  than  three)  is  a  sufficient  guarantee 
against  any  accidents  which  could  prevent  the  proper  exhibition  of 
the  lights.  The  same  objections  might,  with  equal  propriety,  be 
urged  against  revolving,  flashing,  or  any  other  lights  requiring  clock 
machinery ;  yet  such  lights  are  found  on  every  coast  where  lights 
exist  to  any  extent.  A  simple  inspection  of  the  works  of  a  mechani- 
cal lamp  will  convince  any  person  of  common  understanding,  that 
any  mechanic  who  is  capable  of  repairing  the  machinery  for  a  re- 
volving light  is  equally  competent  to  put  in  order  any  lamp  used  in 
light-houses,  and  particularly  those  known  as  mechanical  lamps  with 
concentric  wicks. 

The  oil  of  colza  is  used  exclusively  in  the  French  light-houses, 
M.  Fresnel  says  :  "From  numerous  experiments  it  seems  to  me  that 
these  two  oils  (spermaceti  and  colza)  may  be  employed  with  equal 
success  in  lamps  of  single  or  multiple  wicks. ' ' 

M.  Fresnel' s  preference  for  the  colza  (to  the  sperm  oil)  is  based 
upon  two  reasons  :  first,  the  colza  is  less  expensive  in  France  than 
sperm,  owing  to  the  fact  that  the  vegetable  from  which  this  oil  is 
expressed,  is  cultivated  on  a  very  extended  scale  in  France,  Belgium, 
Holland,  Holstein,  &c. ;  and,  secondly,  the  great  difficulty  in  detect- 
ing impositions  which  may  be  and  are  practised  by  mixing  inferior 
oils  with  the  sperm,  while,  on  the  other  hand,  any  impurities  in  the 
colza  are  very  readily  detected.  No  experiments  have  yet  been 
made  in  France  to  test  fully  which  of  the  two  kinds  of  oil  will  pro- 
duce the  best  light  for  light-house  purposes. 

#•**#**  *  * 

There  is  but  one  floating  light  in  France ;  that  is  constructed  of 
wood,  moored  and  illuminated  after  the  manner,  with  a  few  excep- 
tions, of  those  belonging  to  the  Trinity  Board  in  England.  The 
exceptions  are:  first,  bronze  is  used  in  the  construction  of  the  lantern 
in  the  place  of  iron  ;  and,  secondly,  the  lamps  are  mechanical,  the 
pumps  of  which  are  put  in  play  by  springs  instead  of  the  ordinary 
fountain  lamp.  This  latter,  in  spite  of  the  delicate  machinery  of  the 
lamp,  is  deemed  a  very  decided  improvement,  as  fulfilling  much  more 
fully  the  requirements  of  such  a  lamp,  by  preserving  the  centre  of 
gravity  in  the  same  vertical  during  the  whole  time  of  the  combustion. 


25 


REPORT  OF  THE  TRINITY  HOUSE   ON   THE   RELATIVE   POWER  OF  FRESNEL'S 
AND  THE  REFLECTIVE  SYSTEMS  OF  LIGHTING  LIGHT-HOUSES. 

TRINITY  HOUSE,  London,  E.  C.,  March  5,  1857. 

SIR  :  Having  laid  before  the  Elder  Brethren  your  letter  of  18th 
ultimo,  signifying  the  request  of  the  Lords  of  the  Committee  of  Privy 
Council  for  Trade  to  be  furnished  with  the  results  of  any  experiments 
which  may  have  been  made  by  this  corporation  on  the  relative  power 
of  Fresnel'  s  and  the  Reflective  Systems  of  lighting  light-houses.  1  am 
directed  to  state,  for  their  Lordships'  information,  that  the  reports 
which  have  from  time  to  time  been  made  to  the  Board  by  visiting 
committees  in  allusion  to  the  comparative  effect  of  the  reflective  and 
refractive  principles  when  the  juxtaposition  of  light-houses,  illumi- 
nated therein  respectively,  have  afforded  opportunities  of  comparison, 
lead  to  the  following  conclusions,  viz  : 

That,  although  the  strength  or  power  of  the  reflected  light,  when 
seen  in  the  exact  focus,  may  be  considered  at  least  equal,  if  not 
superior,  to  the  refracted,  the  latter  possesses  the  advantage  of  a 
more  equal  and  uniform  distribution  of  light  over  the  whole  circle  of 
observation,  and  excels  the  reflected  light  when  seen  from  positions 
which  do  not  present  the  advantage  of  full  focus;  it  may  consequently 
be  considered  that  the  reflecting  system  is  fully  as  efficient,  if  not 
superior,  to  the  refracting  for  revolving  lights  ;  and  that  the  latter 
is  superior  for  those  that  are  fixed. 

The  consideration,  however,  which  has  induced  the  Elder  Brethren 
lately  to  adopt  as  a  general  practice  the  use  of  the  refractive  appa- 
ratus is  that  of  its  comparative  economy,  for  although  the  original 
cost  of  a  first  class  apparatus  on  that  principle  considerably  exceeds 
that  of  a  reflective  apparatus  of  the  same  class,  the  consumption  of 
oil  and  the  consequent  expense  of  exhibition  are  materially  less,  and 
the  apparatus  being  altogether  of  a  more  durable  character,  the  cost 
of  repair  and  renovation  is  also  smaller. 

The  reflectors  to  be  fully  efficient  for  their  purpose,  must  be  kept 
in  the  highest  possible  state  of  brilliancy,  and  being  liable  to  become 
dull  or  tarnished  by  the  vapor  which  frequently  arises  in  the  lantern, 
the  constant  application  of  friction  to  their  silvered  surface  is  ren- 
dered necessary,  which  not  only  requires  the  strictest  attention  on 
the  part  of  the  light-keepers,  but  causes  the  gradual  abrasure  of  the 
silver  and  the  consequent  necessity  for  repair  or  renovation. 


26 

Their  Lordships  are  aware  that  a  refractive  apparatus  on  the 
holophotal  principle  has  been  contracted  for  by  Messrs.  Chance,  of 
Birmingham,  for  the  Lundy  Light,  but  which  being  yet  incomplete, 
the  Elder  Brethren  are  unable  to  offer  an  opinion  from  practical 
observation  upon  its  alleged  superiority  over  the  refractive  apparatus 
now  in  general  use. 

I  have  the  honor  to  be,  sir, 

Your  most  obedient  servant, 

P.  H.  BERTHON. 
The  SECRETAEY  MARINE  DEPARTMENT, 
Board  of  Trade. 


REPORT  OF  MESSRS.  STEVENSON,  THE  ENGINEERS  OF  THE  COMMISSIONERS  OF 
NORTHERN  LIGHT-HOUSES,  ON  THE  COMPARATIVE  ELIGIBILITY  OF  THE 
CATOPTRIC  AND  DIOPTRIC  SYSTEMS  OF  ILLUMINATION  OF  LIGHT-  HOUSES. 

In  compliance  with  instructions  from  the  Commissioners,  we  now 
beg  leave  to  report  our  opinion  as  to  the  comparative  merits  of  the 
catoptric  and  dioptric  systems  of  illuminating  light-houses  ;  and  we 
begin  by  stating  the  following  principles,  which  will  be  useful  in 
arriving  at  a  correct  conclusion  : 

We  believe  that  optical  arrangement  to  be  the  most  perfect — 

EIRST.  Which  employs  optical  agents,  consisting  of  materials  that 
absorb  the  smallest  number  of  rays,  and  produce  the  smallest  amount 
of  irregular  scattering  of  the  rays. 

SECOND.  Which  sends  the  greatest  number  of  rays  to  the  eye  of 
the  most  distant  observer,  provided  the  light  is  allowed  to  remain 
sufficiently  long  in  view  to  answer  the  purposes  of  the  navigator. 

THIRD.  Which  produces  the  desired  effect  with  the  smallest  possi- 
ble number  of  optical  agents  ;  and 

FOURTH.  Which  has  no  unnecessary  divergence,  but  which  illumi- 
nates that  arc  only  which  is  absolutely  required  to  be  illuminated. 

If  these  principles  correctly  and  fully  embrace  all  the  essential 
elements  that  must  enter  into  any  comparative  view  of  the  different 
systems  of  light-house  illumination,  it  is  obvious  that,  in  order  to 
discover  whether  the  catoptric  or  dioptric  is  the  better  system,  we 
must  consider,  first,  what  is  the  best  material  to  be  used  in  the  con- 
struction of  the  apparatus  ;  and,  second,  what  is  the  best  arrange- 
ment of  the  optical  agents  which  are  employed. 


27 

We  may  also  premise,  in  order  to  prevent  that  ambiguity  which 
has  gradually  crept  in  from  a  misappropriation  of  certain  terms,  that, 
first,  by  the  term  "Catoptric"  we  wish  to  include  all  optical 
reflecting  apparatus  in  which  the  reflection  is  produced  by  metallic 
surfaces  only;  second,  by  the  term  "Dioptric"  we  include  all  optical 
apparatus  which  consist  of  glass  only,  whether  acting  by  refraction 
only,  or  by  refraction  and  "total,"  or,  as  it  has  been  sometimes 
termed,  "internal"  reflection;  arid,  third,  by  "  Catadioptric "  we 
include  any  combination  of  a  metallic  with  a  glass  optical  agent,  or, 
in  other  words,  any  union  between  the  catoptric  and  dioptric  systems 
as  above  explained. 

THE   MATERIALS    OF   WHICH    THE    DIFFERENT   KINDS    OF    LIGHT-HOUSE 
APPARATUS    CONSIST. 

In  the  catoptric  system  of  illumination  plated  copper      Comparative 

.    *  L  absorption  of 

has  long  had  the  pre-eminence  as  the  best  material  tor  rays  by  glass 
reflectors,  while  in  the  dioptric  glass  is  employed.  In  andmetal- 
contrasting  the  relative  advantages  of  metal  and  glass,  it  must  be 
observed  that  the  loss  of  light  in  metallic  reflection  proceeds  partly 
from  irregular  scattering  of  the  rays,  owing  to  imperfections  in  the 
form  of  the  mirror  and  partly  from  actual  absorption  of  the  rays, 
which  last  depends  mainly  on  the  state  of  the  polish.  When  rays 
of  light  fall  on  a  metallic  mirror,  a  very  considerable  portion  of  them 
are  understood  to  suffer  refraction,  and,  after  entering  the  nearly 
opaque  metal,  they  are  believed  to  be  finally  extinguished  or  anni- 
hilated. In  glass,  on  the  other  hand,  there  is  a  loss  of  light  at  each 
refracting  surface,  and  also  a  loss  by  absorption,  varying  with  the 
thickness  and  color  of  the  material.  Where  the  light  is  both 
refracted  and  reflected  by  prisms  of  glass,  the  reflection  takes  place 
where  the  rays  impinge  at  an  angle  with  the  internal  surface,  less 
than  what  is  termed  the  critical  angle,  where  refraction  becomes 
impossible,  and,  theoretically  at  least,  there  should  not  be  a  single 
ray  of  such  reflected  light  lost,  and  hence  it  is  called  total  reflection. 
It  would  be  tedious  to  quote  extracts  from  writers  as  to  the 
advantages  of  employing  glass  rather  than  inetal  for  altering  the 
direction  of  the  rays  of  light.  We  may  mention  that  Sir  Isaac 
Newton,  Sir  William  Herschel,  Sir  John  Herschel,  Sir  David  Brewster, 
and  others,  have  stated  their  opinions  strongly  on  this  subject.  Sir  John 
Herschel,  for  example,  in  the  article  "Light,"  in  the  "Encyclopaedia 


28 

Metropolitana,"  says  :  "The  reflection  thus  obtained"  (viz:  total  from 
glass)  '  •  far  surpasses  in  brilliancy  what  can  be  obtained  by  other  means, 
from  quicksilver,  for  instance,  or  from  the  most  highly  polished 
metals"  (p.  369.)  Sir  David  Brewster  states  ("Phil.  Journal,"  1832,  p. 
439:) — "I  believe,  however,  on  the  authority  of  the  phenomena  of 
elliptical  polarization,  that  in  silver  nearly  one-half  of  the  reflected  light 
has  entered  the  metal,  and  in  other  metals  a  less  portion,  so  that  we 
may  consider  the  surface  of  every  metal  as  transparent  to  a  certain 
depth — a  fact  which  is  proved  also  by  the  transparency  of  gold  and 
silver  leaf.  It  is  well  known  that  silver, 

polished  by  hammering,  acts  differently  upon  light  from  silver  that 
has  received  a  specular  polish,  and  I  have  elsewhere  expressed  the 
opinion  that  a  parabolic  reflector  of  silvered  copper,  polished  by 
hammering,  will,  from  the  difference  of  density  of  different  parts  of 
the  reflecting  film,  produce  at  the  distance  of  many  miles  a  percep- 
tible scattering  of  the  reflected  rays  similar  to  what  takes  place  in  a 
transparent  fluid  or  solid  or  gaseous  medium." 

Without  quoting  other  authorities  we  shall  refer  to  the  experi- 
ments of  Professor  Potter,  who  has  bestowed  much  attention  to  the 
subject  of  photometry,  and  whose  experiments  have  in  some  respects 
differed  from  those  of  Bonguer  and  Sir  William  Herschel,  and  have 
rather  tended  to  decrease  the  supposed  differences  between  the  light 
lost  by  metallic  reflection  and  that  lost  by  transmission  through  glass. 
He  states,  however,  in  his  "Treatise  on  Optics,"  published  in  1851, 
that  only  about  ^th  of  the  light  is  reflected  when  light  falls  perpen- 
dicularly on  a  surface  of  common  glass,  which,  if  we  suppose  a  similar 
loss  at  the  second  surface,  would  leave  f  gths  to  be  transmitted,  were 
it  not  for  absorption  due  to  the  thickness  and  color  of  the  glass, 
while  he  states,  in  the  same  work,  that  about  one-third  of  the  light 
is  lost  in  a  perpendicular  reflection  from  ordinary  silvered  looking- 
glass,  and  a  little  less  from  highly  polished  speculum  metal.  The 
following  tables  show  the  quantity  of  light  lost  in  reflection  from 
metal,  and  in  transmission  through  glass  at  different  angles  of  inci- 
dence, deduced  from  Professor  Potter's  experiments: 


29 


TABLE  OF  EXPERIMENTS  ON  METALLIC 
REFLECTION-. 

TABLE  OF  EXPERIMENTS  ON  Loss  OF 
LIGHT  IN  TRANSMISSION  THROUGH 
PLATE  GLASS  ^-INCH  IN  THICKNESS. 

Angles 
of  Incidence. 

Quantity  lost  by 
Reflection,  &c. 

Angles 
of  Incidence. 

Loss  in 
Transmission. 

.... 

0° 

•086 

10° 

•314 

10° 

•092 

20° 

•305 

20° 

30° 

•334 

30° 

•094 

40° 

•332 

40° 

•106 

50° 

•346 

50° 

•  125 

60° 

•351 

60° 

•161 

70° 

•349 

70° 

•254 

Now,  whatever  loss  there  may  be  from  the  passage  of  the  light 
through  glass  of  greater  thickness  than  that  employed  in  these 
experiments,  it  is  obvious  that  there  can  be  no  appreciable  loss 
caused  by  the  refractions  at  the  angles  of  incidence  on  the  first  order 
glass  prisms  which  are  in  use  in  light-houses,  as  these  vary  from 
7°  30'  to  45°,  and  in  the  lens  from  0°  to  under  30°,  and  therefore 
fall  wholly  within  the  limits  of  the  above  experiments,  which,  in 
addition  to  the  loss  by  refractions,  include  that  of  the  absorption  due 
to  a  thickness  of  i-th  inch. 

With  regard  to  the  absorption  due  to  the  passage  of  light  through 
a  thick  prism,  we  have  only  a  few  experiments  of  Professor  Potter  to 
refer  to.  In  the  Phil.  Magazine  for  1832  he  first  demonstrates 
experimentally  the  important  fact  that,  as  had  been  generally  supposed, 
there  is  no  loss  of  light  by  total  re/lection.  The  whole  loss  is  therefore 
due  to  the  two  refracting  surfaces,  and  to  the  absorption  in  passing 
through  the  glass.  His  experiments  on  the  amount  of  these  are  as 
follows:  the  loss  of  light  due  to  every  cause  in  traversing  a  totally 
reflecting  prism  of  glass  of  the  thickness  of  1-98  inch,  averaged  '234, 
where  unity  represents  the  whole  incident  light.  The  amount  of 
glass  traversed  in  these  experiments  is  very  nearly  the  same  as  in 
the  more  modern  light-house  prisms,  so  that  the  above  results  become 
quite  applicable  to  our  purpose.  We  also  made  some  observations 
on  pieces  ot  straight  rectangular  prisms  of  the  same  size  and  quality 


30 

as  is  used  in  light-houses,  and  by  means  of  Professor  Potter's  photo- 
meter we  obtained  results  somewhat  higher  than  those  just  given. 
The  results  will  be  found  detailed  in  Appendix  No.  1.  It  is  merely 
necessary  here  to  state  that,  with  31  experiments,  and  with  four 
different  observers,  we  got  a  mean  value  of  "805  for  the  amount  of 
light  transmitted.  We  are  far,  however,  from  wishing  to  place  our 
results  on  an  equality  with  those  of  Professor  Potter,  whose  great 
experience  and  accuracy  in  photometry  are  so  generally  acknowl- 
edged, and  we  are  therefore  quite  content  to  adopt  the  lower  results 
which  he  has  obtained.  It  will  be  seen  from  his  experiments,  which 
have  already  been  quoted,  that  by  reflection  from  highly  polished 
specula,  within  the  limits  of  from  10°  to  70°  of  incidence,  the  loss  of 
light  varies  from  -31  to  "35;  while  the  loss  by  total  reflection  is  only 
about  '23.  Here  then  is  a  clear  gain  of  one-tenth  in  favor  of  glass 
over  metal;  or  if  we  took  our  own  results,  there  would  be  a  some- 
what greater  gain.  But  we  must  now  notice  a  highly  important 
allowance  which  has  to  be  made  in  this  case.  Professor  Kelland  has 
kindly  informed  us  that  Professor  Potter  considers  the  results  of  his 
experiments  on  metallic  reflection  "quite  inapplicable  to  light-houses, 
as  the  polish  in  his  mirrors  was  such  that  the  surface  could  not  be 
seen  when  held  near  the  flame  of  a  candle,  but  appeared  like  a  hole 
in  the  side  of  a  dark  box.  The  polish  of  a  light-house  reflector," 
he  adds,  "could  never  be  kept  up  to  this  state."  It  would,  indeed, 
be  impossible  to  give  such  a  polish  even  to  a  new  reflector.  The 
manner  in  which  specula  are  polished,  and  by  which  alone  such  a 
perfect  surface  is  attainable,  is  entirely  inapplicable  to  a  soft  metal 
like  silver;  and  neither  can  such  a  method  of  working  be  employed 
for  any  curve  which  varies  much  from  a  circular  segment. 

It  clearly  appears,  then,  that  whatever  may  be  the  comparative 
gain  due  to  the  employment  of  total  over  metallic  reflection,  and  we 
think  there  is  every  reason  to  believe  it  large,  at  least  enough  has 
been  said  clearly  to  establish  the  superiority  of  glass  over  metal,  as 
a  material  for  constructing  light-house  apparatus,  so  long  as  the  inci- 
dence of  the  rays  is  not  too  oblique.  It  must  also  be  observed  that 
the  loss  from  absorption  may  be  reduced  almost  indefinitely  by 
increasing  the  number,  and  thus  reducing  the  size  of  the  prisms 
which  are  employed. 

In  Appendix  No.  II  will  be  found  a  number  of  experiments  which 
we  have  made  on  the  reflecting  power  of  silver  plate,  polished  in  the 
same  manner  as  a  light-house  reflector.  From  these  it  will  be  seen 


31 

that  not  much  more  than  one  half  (-556)  of  the  light  incident  was 
reflected,  a  result  which  tallies  with  the  statement  of  Sir  David 
Brewster  to  that  effect  in  his  "Treatise  on  Optics."*  If  we  assume 
the  result  as  correct,  and  compare  it  with  Professor  Potter's  valua- 
tion of  a  totally  reflecting  prism,  we  shall  have  a  gain  of  two-tenths 
(•210)  in  favor  of  glass  over  metal;  or  if  we  compare  it  with  our  own 
experiments,  we  should  have  a  gain  of  almost  one-fourth  (-249)  by 
employing  glass. 

Before  leaving  the  subject  of  the  material  to  be  employed  in  light- 
house apparatus,  we  must  yet  notice  some  further  advantages  which 
are  peculiar  to  glass. 

Curves  formed  in  glass  certainly  admit  of  much  greater  accuracy 
in  form  than  those  of  metallic  reflectors.  In  the  one  case  the  result 
is  affected  by  a  very  gradual  process  of  grinding  by  means  of  unerring 
machinery  of  a  rigid  and  unalterable  construction;  while  in  the  other 
case  the  result  is  attained  by  a  comparatively  rude  tentative  manual 
process,  and  subject  therefore  to  all  the  imperfections  to  which  such 
methods  of  working  are  obviously  liable.  The  polish,  too,  on  which 
so  very  much  depends,  is  in  the  glass  apparatus,  given  once  for  all  by 
the  finely  constructed  machinery  of  the  manufacturer,  whereas  the 
metallic  polish  is  constantly  undergoing  deterioration  from  atmos- 
pheric oxidation,  and  requires  to  have  its  brilliancy  daily  renewed 
by  a  succession  of  different  light-keepers,  from  the  less  skillful  of 
whom  it  may  receive  ineradicable  scratches  and  permanent  injuries. 
Thus  while  the  glass  never  loses  its  correct  form,  the  metallic  polish 
may  be  deteriorated  and  the  curve  of  the  mirror  may  be  materially 
altered,  although  the  existence  of  injuries  and  changes  of  form  may 
never  be  suspected. 

It  is  still,  however,  a  possible  case  that  improvements  may  be 
made  on  metallic  reflectors,  or  that  other  suitable  metals  or  metallic 
combinations  may  be  discovered  which  are  capable  of  receiving  a 
superior  and  more  lasting  polish  than  silver.  But  unless  it  can  be 
shown  that  there  is  indeed  a  very  great  gain  from  the  use  of  the 
metallic  reflection,  we  shall  still  remain  decidedly  of  opinion  that, 
irrespective  altogether  of  the  superiority  of  glass  viewed  as  a  material, 

0  "The  great  value  of  such  a  mirror  "  (one  acting  by  total  reflection)  "  is  that  as  the 
incident  rays  fall  upon  A.  C."  (the  reflecting  surface)  "  at  an  angle  greater  than  that  at 
which  total  reflection  commences,  they  will  all  suffer  total  reflection,  and  not  a  ray  will  be 
lost.  Whereas  in  the  best  metallic  speculum  nearly  half  of  the  light  is  lost.  "—Treatise  on  Optics, 
by  Sir  D.  Brewster.  London,  1831. 


32 

it  possesses  other  peculiar  advantages  which  render  it  decidedly 
more  eligible  as  an  optical  agent.  This  will  appear  more  fully  from 
a  consideration  of  the  next  subject  which  we  propose  to  discuss,  viz  : 
What  is  the  best  optical  arrangement  for  light-house  illumination  ? 

OPTICAL   ARRANGEMENT   OF   APPARATUS. 

Fixed  lights.  Jt  is  obvious,  as  appears  from  our  second  general  pos- 
tulate (vide  p.  26,)  that  no  apparatus  can  be  regarded  as  the  best 
which  suffers  any  portion  of  the  diverging  rays  which  proceed  from 
a  flame  to  escape  into  the  atmosphere  without  being  parallelized  in 
the  directions  required  by  the  mariner,  for  such  rays  are  altogether 
lost.  In  Fresnel's  fixed  light  apparatus,  where  the  object  is  to 
illuminate  constantly  the  entire  horizon,  the  whole  sphere  of  light  is 
emitted  parallel  to  the  horizon  ;  and  as  the  apparatus  consists  only 
of  a  cylindric  refracting  hoop,  and  totally  reflecting  prisms,  it  pro- 
duces its  effect  by  the  simplest  conceivable  combination  of  the  best 
optical  agents  ;  we  are  therefore  of  opinion  that  it  cannot  be  sur- 
passed, and  must  be  regarded  as  the  optimum  form  for  fixed  lights 
in  insular  stations.  In  narrow  Sounds,  where  it  is  desirable  to  alter 
the  intensity  of  the  light  in  different  azimuths  in  proportion  to  the 
different  distances  to  which  the  light  requires  to  be  seen,  we  con- 
sider the  holophotal  condensing  apparatus  to  be  the  proper  arrange- 
ment. This  construction,  as  the  Board  is  aware,  is  now  being 
adopted  in  several  of  the  Sound  lights  on  the  west  of  Scotland. 

For  a  revolving  light,  it  is  desirable  that  only  a  small 
light  fitted  horizontal  arc  should  be  illuminated  by  each  flash  ;  and 
Sde  mien?  'li  is  obvious  that  that  arrangement  must  be  the  best 
lamps  and  which,  without  employing  unnecessary  optical  agents 
jr^untecTon  (1j7  which,  as  has  already  been  seen,  much  light  is  lost,) 
a  revolving  condenses  the  whole  sphere  of  diverging  rays  which  pro- 
ceed from  the  flame  into  the  required  arc  or  arcs  of  illu- 
mination. The  only  arrangement  with  which  we  are  acquainted  that 
fulfils  these  conditions,  is  that  which  has  been  termed  the  holophotal, 
which  was  first  adopted  in  a  harbor  light  at  Peterhead.  in  1849. 

In  the  catadioptric  form,  it  parallelizes  the  whole  sphere 
Catoptric         „    ,.  r 

andcatadiop-     ol  diverging  rays  into  one  beam  by  means  of  a  certain 

ments"™1^"     UI"on  °^  parabolic  and  spherical  metallic  mirrors  and  a 

lens.     These  three  instruments  must  be  so  combined  as 

in  no  way  to  interfere  with  the  proper  action  of  each  other,  and  in 

such  a  manner  that  all  shall  have  one  common  focus  situate  in  the 


33 

centre  of  the  flame  of  the  lamp.  The  parabolic  reflectors,  commonly 
used  in  light-houses,  suffer  not  much  short  of  one  half  of  the  whole 
sphere  of  diverging  rays  to  escape  uselessly  past  the  lips  of  the 
reflector.  In  the  reflector- proposed  by  Mr.  A.  Gordon,  in  1847, 
there  is  also  no  attempt  made  to  parallelize  the  rays  which  are  imme- 
diately in  front  of  the  flame,  and  the  surface  behind  the  parameter  of 
that  reflector  is  so  exceedingly  small,  that  one  half  of  the  whole 
sphere  of  rays  seems  to  fall  upon  a  surface  nowhere  more  than  about 
one  inch  and  a  half  from  the  circumference  of  the  flame.  The  effect 
of  this  arrangement,  which  in  other  respects  is  a  step  in  the  right 
direction,  is,  practically  speaking,  to  throw  away  perhaps  nearly  one 
half  of  the  whole  sphere  of  rays.  For,  in  addition  to  the  light  which 
is  lost  in  front  of  the  lamp,  and  independent  altogether  of  the  enor- 
mous aberrations  which  must  result  from  the  slightest  imperfections 
in  the  original  form  of  what  is,  in  this  instrument,  a  most  critical  part 
of  the  apparatus,  the  divergence  produced  by  a  flame  of  one  inch  in 
diameter  is,  with  this  instrument,  no  less  than  about  sixty  degrees. 
Now,  even  although  it  were  desirable,  which  it  never  is,  to  illuminate 
so  great  a  horizontal  arc  by  each  flash  of  a  revolving  light,  it  is  per- 
fectly obvious  that  there  can  be  no  possible  use  of  any  divergence  in 
the  vertical  plane  above  the  horizon.  From  this  it  will  be  seen  that 
such  an  apparatus  cannot  be  regarded  as  at  all  perfect.  Mr.  "W. 
Barlow  has  proposed  (Royal  Society  Transactions,  1837,  p.  215)  to 
increase  the  illuminating  power  of  a  reflector  by  placing  a  spherical 
reflector  in  front  of  the  flame,  so  as  to  intercept  the  rays  which  would 
otherwise  be  lost,  and  to  return  them  back  again  through  the  light 
itself.  This  ingenious  plan,  though  otherwise  largely  economical  of 
light,  necessarily  renders  wholly  useless  that  portion  of  the  reflector 
which  is  opposite  to  it,  and  it  also  occasions  the  loss  by  absorption 
of  a  considerable  portion  of  the  front  rays.  A  far  more  complete 
optical  arrangement  is  that  which  was  proposed  so  far  back  as  1812 
by  Sir  David  Brewster,  and  afterwards  introduced  by  A.  Fresnel  in 
his  revolving  lights.  By  Sir  David' s  plan,  the  whole  sphere  of  rays 
was  usefully  employed,  and  the  excessive  amount  of  divergence  to 
which  we  have  just  referred  was  avoided.  It  labors,  however,  under 
the  serious  disadvantage  of  employing  an  unnecessary  optical  agent, 
which  is  obviated  by  the  holophotal  arrangement. 

The    holophotal    dioptric    arrangement  may   also   be 
adopted  where  independent  burners  are  used.     In  this 
case   the  whole   apparatus   consists   of  refractors,   and 
3 


34 

totally  reflecting  prisms  of  glass  made  of  a  peculiar  form,  which 
prisms  were  first  used  in  light-houses  on  our  recommendation  at 
Horsburg  revolving  light  in  1851.  When  it  is  necessary  to  establish 
lights  at  distant  and  inaccessible  places,  we  consider  the  holophotal 
dioptric  system,  with  independent  burners,  to  be  the  most  eligible, 
and  we  are  at  present  getting  apparatus  on  this  principle  for  the 
Board  of  Works  of  Newfoundland.  Glass  is,  however,  generally 
adopted  in  first  order  apparatus,  having  a  single  central  burner,  with 
the  frame  work  of  glass  revolving  round  it.  We  shall  now,  there- 
fore, refer  to  that  system. 

In  the  dioptric  system  on  the  large  scale  there  is  gen- 
tem  with  one  erally,  as  has  just  been  stated,  only  one  central  burner, 
central  burn-  and  the  light  ig  con(jensed  into  such  number  of  parallel 
beams  as  may  be  found  most  convenient  by  the  action 
of  apparatus  revolving  round  the  central  flame.  We  have  already 
shown  that  the  holophotal  arrangements  are  preferable  in  the  smaller 
class  of  apparatus,  and  it  will  at  once  appear  that  the  same  must  be 
the  case  on  the  large  scale.  The  first-class  dioptric  holophotal  appa- 
ratus, consisting  of  lenses  and  totally  reflecting  prisms,  similar  to 
those  of  Horsburg,  already  referred  to,  produces  its  effects  by  means 
of  a  single  optical  agent,  which  is  not  the  case  in  any  other  arrange- 
ment. The  revolving  apparatus  of  Fresnel,  for  example,  is  far  from 
being  (like  his  fixed  light)  a  perfect  arrangement.  In  it  we  find  the 
light  which  passes  below  the  lenses  distributed  all  round  the  horizon, 
instead  of  within  the  arc  of  useful  illumination,  and  the  light  which 
passes  above  the  lenses  is  subjected  to  the  action  of  inclined  mirrors 
and  lenses,  by  which  the  illustrious  inventor  himself  admits  that  there 
is  a  loss  of  about  half  of  the  light  incident  on  that  portion  of  the 
apparatus.  In  Fresnel' s  fixed  light  varied  by  flashes  there  is  a  simi- 
lar employment  of  two  optical  agents,  whereas  there  is  but  one  in  the 
holophotal  system.  In  the  beautifully  finished  first  order  fixed  light 
varied  by  flashes  which  was  exhibited  in  the  Great  Britain  exhibition 
of  1851  as  a  patented  invention,  and  which  was  of  French  manufac- 
ture, there  was  a  similar  unnecessary  reduplication ;  large  cylindric 
refracting  panels  being  placed  in  front  of  the  ordinary  fixed  light 
prisms.  While  in  the  corresponding  holophotal  arrangement,  on  the 
contrary,  the  same  effect  is  produced  by  the  action  of  a  single  optical 
agent. 


35 

But  it  is  well  known  that  the  gravest  objection  to  the 
dioptric  system  of  lights  as  originally  constructed  is  the  tage  of  diop- 
smallness  of  its  divergence.  The  great  annular  lens  has  tric  system- 
a  divergence  not  exceeding  about  5°  9',  whereas  it  may  be  desirable 
that  it  should  in  certain  cases  have  perhaps  twice  this  divergence. 
In  the  flashing  holophotal  light  of  the  first  order,  at  North  Konald- 
shay,  (which  was  the  first  apparatus  of  the  kind  constructed,)  the 
horizontal  divergence  was  accordingly  increased  by  placing  the  panels 
of  totally  reflecting  prisms  with  their  axis  3°  30'  on  each  side  of  that 
of  the  central  lens,  and  this  amount  of  divergence  has  been  found  to 
be  amply  sufficient.  Were  it  considered  necessary  for  any  purpose, 
as,  for  instance,  in  a  revolving  light  with  a  long  period  of  intervening 
darkness,  to  increase  the  divergence  still  further,  nothing  can  be 
easier  than  to  adopt  the  spherico-cylindric  form  of  lens  recommended 
by  Mr.  Thomas  Stevenson,  in  the  Edinburgh  Phil.  Journal  for  1856.* 

That  apparatus,  then,  is  obviously  the  best  which  condenses  the 
rays  with  the  minimum  amount  of  divergence  in  every  plane,  provid- 
ing always  that  it  is  easy,  as  has  been  shown  in  the  case  of  the  diop- 
tric apparatus,  to  increase  by  a  slight  alteration  in  the  arrangement 
the  natural  divergence  just  so  far  only,  and  in  such  planes  only  as 
may  be  required.  It  is,  therefore,  only  with  apparatus  such  as  has 
been  described,  possessing  this  limited  divergence,  that  the  light 
is  prevented  from  being  uselessly  projected  upwards  towards  the 
clouds.  • 

Having  thus  endeavored  to  show  the  relative  merits      Ugeful  effect 

of  the  different  materials,  and  different  forms  of  appa-     of    different 

systems, 
ratus,  we  will  turn  for  a  moment  to  the  experiments 

which  have  been  made  with  the  view  of  comparing  the  useful  effects 
of  different  apparatus.  We  need  hardly  advert  to  the  striking  ad- 
vantage of  Fresnel's  fixed  dioptric  apparatus  of  glass  over  the  former 

°  The  apparent  superiority  of  the  metallic  mirror  in  respect  of  divergence  is,  in  reality, 
as  has  been  already  shown,  a  great  evil,  for  although  such  an  amount  of  divergence  in  the 
horizontal  plane,  or  in  the  vertical  plane  below  the  horizon,  may  be  very  well,  yet  it  is  a 
positive  loss  in  the  vertical  plane  above  the  horizon.  But  in  the  dioptric  system,  if  it  were 
ever  found  necessary  under  some  peculiar  circumstances  to  increase  the  vertical  divergence 
bdow  the  horizon,  this  could  be  easily  done  by  giving  the  whole  or  part  of  the  apparatus  a 
slight  dip  forward.  We  have  not,  however,  in  our  practice  ever  found  it  necessary  to 
adopt  this  plan.  Reflectors,  on  the  other  hand,  cannot  be  dipped  so  as  to  save  the  light 
passing  above  the  horizon,  because  that  would  entail  the  loss  of  the  light  passing  below 
the  horizon,  which  would  be  thrown  close  to  the  light-house  tower,  where  it  is  not 
required. 


36 

system  of  reflectors,  as  we  can  scarcely  imagine  the  existence  of  any 
doubt  now  as  to  its  superiority.     We  will,  therefore,   confine  our 
attention  to  the  subject  of  revolving  lights.     The  numerous  experi- 
ments which  were  instituted  many  years  ago  by  the  Board  of  North- 
ern Lights  at  Gullan  proved  that  a  first-order  lens  equalled  in  effect 
that  of  from  seven  to  nine  reflectors.     The  reflectors  which  were 
experimented  upon  were  those  which  were  then  in  general  use  by 
the  Board,  and  it  may  no  doubt  be  objected  that  had  those  reflectors 
been  rendered  holophotal  the  result  would  have  been  different.     In 
proof  of  this  we  may  mention  that  in  1850  a  brass  holophotal  reflector 
was  tried  against  a  Northern  Light  silvered  reflector  at  Gullan,  and 
was  viewed  by  observers  stationed  at  distances  of  seven  and  nine 
miles,  who  were  purposely  kept  in  ignorance  of  the  different  arrange- 
ments, and  in  every  instance  the  brass  holophotal  reflector  had  the 
advantage,  and  on  one  occasion  during  fog  it  only  ivas  visible.     But  it 
must  be  recollected  that  since  the  date  of  the  Gullan  experiments 
the  lenticular  system  has  acquired  at  least  a  corresponding  advantage 
over  the  old  revolving  light  of  Fresnel,  by  the  adaptation  of  the 
holophotal  arrangement  to  lights  of  the  first  order.     We  may,  there- 
fore, for  want  of  other  experiments,  conclude  (with  the  high  proba- 
bility of  being  far  within  the  mark)  that  now,  as  formerly,  the  illu- 
minating power  of  the  most  perfect  kind  of  lenticular  apparatus  of 
the  first  order,  and  the  most  perfect  kind  of  parabolic  reflector,  are 
injthe  ratio  of  at  least  eight  to  one.     Now,  however  suitable  in  many 
situations  and  for  lights  of  subordinate  importance  the  dia-catoptric 
system  may  be,  we  are  strongly  of  opinion  that  for  great  sea  lights 
the  dioptric  is  the  far  preferable  arrangement.     The  advantages  of 
the  dioptric  system  will  more  plainly  appear  if  we  keep  strictly  in 
view  that  the  grand  desideratum  for  sea  lights  is  an  augmentation  of 
power,  so  as  to  give  the  mariner  as  great  an  "offing"  as  possible. 
Suppose,  for  example,  we  wish  to  produce  by  reflectors  the  effect  of 
eight  first-order  lenses,  we  should  require  to  provide  a  lantern  capa- 
ble of  accommodating  from  56  to  72  reflectors,  and  if  so  great  a  num- 
ber of  independent  reflectors  is  admitted  to  be  all  but  impracticable, 
and  we  fall  back  upon  one  central  four  wicked  lamp  surrounded  by 
tiers  of  metallic  reflectors,  we  shall  not  have  gained  anything  by  the 
change,  for  the  loss  of  light  between  the  interstices  which  separate 
the  different  portions  of  the  mirrors  will  be  great,  and  the  errors  in 
position  due  to  the  daily  polishing  of  so  great  a  system  of  mirrors, 
and  the  amount  of  labor  that  will  be  required,  are  such  as  to  render 


37 

it  necessary  to  have  recourse  to  silvered  glass.  If  such  were  the 
case  we  should  have  the  loss  of  light  due  to  the  metallic  reflection, 
and  also  to  two  refractions  at  the  surfaces  of  the  glass.  Arago  found 
by  actual  trial  that  the  useful  effect  of  such  a  system  of  reflectors, 
when  compared  with  the  totally  reflecting  prisms  for  Skerryvore 
light-house,  were  as  1  to  1-61.  M.  Fresnel  also  found  the  effect  of 
a  metallic  reflector  was  to  that  of  a  catadioptric  apparatus  of  the 
same  size  in  the  ratio  of  about  1  to  2. 

For  first-class  lights,  then,  the  case  seems  to  be  very  clear  ;  and, 
in  connexion  with  this  part  of  the  subject,  we  would  refer  to  the 
Appendix  No.  III.  for  the  extract  from  a  letter  addressed  to  the 
Hydrographer  of  the  Admiralty,  regarding  the  erection  of  great  sea 
lights  on  a  gigantic  scale,  for  increasing  the  safety  of  over-sea  vessels. 
Were  the  construction  of  such  sea  beacons  resolved  on,  there  can  be 
no  doubt  that  the  only  practicable  manner  (in  the  present  state  of 
our  knowledge  as  to  the  sources  of  light)  in  which  the  necessary 
power  could  be  secured,  would  be  by  means  of  the  dioptric  system. 

It  may  not  be  out  of  place,  as  having  an  important  bearing  on  the 
subject,  to  mention,  in  conclusion,  that  in  France,  Holland,  and 
Spain,  and  we  believe  in  most  other  commercial  countries,  the  prefer- 
l-«nce  has  been  already  given  to  the  dioptric  system.  In  particular, 
|aie  American  Government,  so  lately  as  1852,  after  having  devoted 
most  careful  attention  to  the  whole  subject,  and  after  having  accu- 
mulated from  different  countries  and  from  various  quarters  a  great 
amount  of  information,  which  has  been  published  at  full  length, 
stated  the  following  as  the  conclusion  of  their  labors  (page  13  of  their 
Report)  :  ' '  That  the  Fresnel  or  lens  system,  modified  in  special 
cases  by  the  holophotal  apparatus  of  Mr.  Thomas  Stevenson,  be 
adopted  as  the  illuminating  apparatus  for  the  lights  of  the  United 
States,  to  embrace  all  new  lights  now  or  hereafter  authorized,  and  all 
lights  requiring  to  be  renovated  either  by  reason  of  deficient  power, 
or  of  defective  apparatus." 

(Signed)  D.  &  T.  STEVENSON. 

EDINBURGH,  May  6,  1857. 


APPENDIX. 


No.  I. 

TABLE  showing  the  AMOUNT  of  LIGHT  AVAILABLE,  after  passing  through 
a  totally  REFLECTING  PRISM,  as  prepared  for  ordinary  LIGHT-HOUSE 
purposes.  (Angle  of  incidence  on  external  surface  =  39°;  length 
of  passage  through  glass  =  2-6  inches.) 

The  results  are  expressed  in  a  fractional  form,  direct  light  being 
assumed  =  1. 


AMOUNT  OP 
AVAILABLE  LIGHT. 

REMARKS. 

•824 

Mean  of  4 

observations. 

•  809 

"     of  3 

» 

•  873 

"     of  4 

ii 

•  804 

"     of  3 

1  1 

•869 

"     of  6 

1  1 

•  812 

"     of  4 

1  1 

•  734 

"     of  3 

<  t 

•  716 

"     of  3 

(  < 

•  805 

General  mean 
by  four  difft 

of  31  trials  made 
rent  observers. 

NOTE. — The  last  two  sets  of  observations  appear  to  be  decidedly 
too  low,  but  they  are  inserted,  as  no  error  in  the  adjustment  of  the 
apparatus  was  detected  at  the  time. 


39 


No.  II. 

TABLE  showing  the  AMOUNT  of  LIGHT  AVAILABLE  after  REFLECTION 
from  surfaces  of  silver,  polished  in  the  same  manner  as  LIGHT-HOUSE 
REFLECTORS.  (Angle  of  incidence  45°.) 

The  results  are  given  in  a  fractional  form,  direct  ligh  being  =  1°. 


AMOUNT  OF 
AVAILABLE  LIGHT. 

REMARKS. 

•  520 

Mean  of  3  observations. 

•501 

"     of  3 

•620 

11     of  3             " 

•676 

11     of  5             « 

•  644 

"     of  4 

•560 

"     of  4             " 

•  730* 

"     of  4 

•380* 

"     of  3             "   1 

| 

•517 

u     Of  4             u 

•496 

"     of  4             " 

ll 

•  472 

"     of  4             u 

.556 

(  General  mean  of  41  trials  by 
|      three  different  observers. 

•556 

(  General  mean    excluding   the 
(      observations  marked  with  *. 

NOTE. — These  experiments  were  made  with  two  pieces  of  ham- 
mered silver  plate,  made  as  flat  as  possible,  and  as  the  polish  seemed 
to  be  equally  good  in  each,  the  difference  of  effect  must  have  been 
due  to  some  slight  curvature,  probably  in  opposite  directions.  "We 
believe,  however,  that  the  mean  cannot  be  far  from  the  truth. 


a  These  experiments,  which  were  made  successively  by  the  same  observer,  appear  to  be 
inaccurate,  but  the  cause  has  escaped  detection. 


40 
No.  III. 

OCEAN  LIGHTS. 

Extract  from  a  letter,  dated  December  27,  1855,  to  Captain  Washington, 
Hydrographer  to  Hue,  Admiralty,  ly  Thomas  Stevenson,  C.  E.,  in 
reference  to  the  question  of  the  characteristics  for  distinguishing  Lights. 

*  *  *  "What  we  want  is  powerful  apparatus,  not  intri- 
cate distinctions.  To  be  enabled  to  see  a  light  in  a  thick  night, 
though  it  be  only  half  a  mile  further  than  at  present,  may  be  of  in- 
calculable moment.  If,  therefore,  we  can  increase  the  power  of  our 
lights  so  as  to  make  them  pierce  the  gloom  but  that  fraction  of  a  mile 
further  than  they  do  at  present,  we  are  moving  in  the  right  direction. 
On  that  small  amount  of  extra  offing  hundreds  of  lives  may  depend. 
This  subject  has  been  much  before  my  mind  lately,  and  I  am  of  opin- 
on  that  there  ought  to  be  constructed  perhaps  three  or  four  great 
Ocean  Lights,  situate  on  different  points  in  England,  Ireland,  and 
Scotland,  facing  the  Atlantic,  and  possessing  optical  powers  which 
would  greatly  transcend  anything  as  yet  attempted,  or  than  is  indeed 
required  in  many  ordinary  cases,  where  a  smaller  offing  is  needed ; 
although  in  all  cases  superior  power  constitutes  in  reality  superior 
safety.  Such  lights  as  I  have  mentioned  would  form  noble  protec- 
tions for  homeward  bound  vessels  by  giving  them  longer  offings. 
For  such  purposes  I  would  propose  of  course  revolving  lights  as  being 
most  powerful,  and  I  would  adopt  for  them  first-order  holophotal 
apparatus  arrang-ed  in  a  manner  not  yet  attempted,  but  which  would 
enormously  increase  the  effect,  without  necessarily  involving  a  greater 
consumption  of  oil.  I  must,  however,  reserve  troubling  you  with 
this  scheme  at  present.  I  intend,  however,  to  devote  my  first  leisure 
time  to  this  matter,  when  I  shall  probably  take  the  liberty  of  seeking 
your  advice  on  the  subject." 


LIGHT-HOUSE  PAPERS, 


PLAN 


DISTINGUISHING  SEACOAST  AND  OTHER  LIGHTS, 

BY    OCCULTATIONS. 


BY  CHARLES  BABBAGE,  ESQ.,  &c.,  &c.,  &c., 

LONDON. 


RESOLUTION  OF  THANKS  TO  CHARLES  BABBAGE,  ESQ. 

Resolved,  That  the  Light-house  Board  of  the  United  States  have 
received,  with  much  gratification,  and  have  examined  with  great  in- 
terest, the  plan  of  distinguishing  seacoast  and  other  lights  by  occul- 
tations,  proposed  by  CHARLES  BABBAGE,  Esq.,  of  London,  and  kindly 
communicated  to  them,  and  will  use  every  endeavor  to  have  a  full 
trial  made  of  the  method,  which,  in  their  opinion,  promises  such 
great  advantages  to  the  navigation  of  the  world. 

Resolved,  That  the  thanks  of  the  Board  are  hereby  tendered  to 
CHARLES  BABBAGE,  Esq.,  for  his  communication,  made  on  the  invita- 
tion of  one  of  its  members. 

Adopted  unanimously,  November  26th,  1851. 

WM.  BRANFORD  SHUBRICK, 

President. 

THORNTON  A.  JENKINS,  Secretary. 


44 


NOTES    RESPECTING    LIGHT-HOUSES, 

BY   CHARLES  BABBAGE,  ESQ. 

The  object  of  these  notes  is  to  point  out  certain  improvements  in 
the  use  of  existing  light-houses,  by  which  it  shall  become  almost  im- 
possible — 

1st.  To  mistake  any  casual  light,  on  shore  or  at  sea,  for  a  light- 
house. 

2d.  Ever  to  mistake  one  light-house  for  another. 

The  plan  requires,  in  most  instances,  no  change  in  the  optical 
means  at  present  used  for  condensing  and  directing  the  illumination 
of  light-houses.  It  adds  slightly  to  the  facility  of  observing  them 
at  great  distances;  and,  from  its  simplicity  and  generality,  is  equally 
adapted  to  the  use  of  all  countries.  Revolving  lights  must  become 
fixed  |  but  the  mechanism  already  existing  for  their  rotation  may, 
with  little  alteration,  be  employed  for  the  motions  required  by  the 
new  system. 

The  principle  by  which  these  objects  are  to  be  accomplished,  is 
to  — 

Make  each  light-house  repeat  its  own  number  continually  during  the 
wliole  time  it  is  lighted. 

This  is  accomplished  by  enclosing  the  upper  part  of  the  glass 
cylinder  of  the  Argand  burner  by  a  thin  tube  of  tin  or  brass,  which, 
when  made  to  descend  slowly  before  the  flame,  and  then  allowed 
suddenly  to  start  back,  will  cause  an  occultation  and  reappearance 
of  the  light. 

The  number  belonging  to  a  light-house  may  be  thus  indicated  to 
distant  vessels.  Take  as  example  243  : 

1.  Let  there  be  two  occultations. 

2.  A  short  pause. 

3.  Four  occultations. 

4.  A.  short  pause. 

5.  Three  occultations. 

6.  A  longer  interval  of  time. 

This  system  of  occultations  must  be  repeated  all  night  by  proper 
mechanism. 


45 

The  rapidity  of  the  occultations  themselves,  the  length  of  the 
pauses  between  the  units  and  the  tens,  and  between  the  tens  and 
hundreds,  as  well  as  the  duration  of  the  long  interval  of  time  which 
marks  the  termination  of  the  number,  must  be  made  the  subject  of 
experiment. 

A  light  has  been  already  used  as  an  illustration,  in  which  the  oc- 
cultations occurred  at  intervals  of  one  second  ;  the  pause  occupied 
four  and  the  long  interval  ten  seconds.  The  pause  was  thought  to 
be  unnecessarily  long,  and  was  diminished.  Whatever  may  be  the 
times  ultimately  adopted,  the  experiments  already  made  render  it 
improbable  that  the  average  time  required  by  a  light-house  for  re- 
peating its  number,  should  amount  to  one  minute. 

It  is  by  no  means  necessary  that  the  counting  of  the  number  of  a 
light-house  should  commence  with  the  digit  which  expresses  hun- 
dreds. No  greater  amount  of  time  would  have  elapsed,  if,  in  the 
above  instance,  the  observer  had  commenced  with  counting  the 
unit's  figure.  It  would  then  have  read  thus  :  (3  occultations,)  long 
interval,  (2  occultions,)  pause,  (4  occultions,)  pause. 

But,  since  the  long  interval  denotes  the  commencement  of  a  num- 
ber, it  is  already  apparent  that  the  number  of  the  light-house  is  243 
and  not  324. 

In  order  still  further  to  prevent  mistakes  arising  from  an  acci- 
dental error  in  counting  the  number  of  occultations,  it  will  be  con- 
venient to  establish  another  principle  for  the  purpose  of  numbering 
the  light-houses. 

Light-houses  must  not  be  numbered  in  the  order  of  their  position.  But 
every  light-house  must  have  such  a  number  assigned  to  it,  that  no  digit 
occurring  in  the  number  denoting  the  several  light-houses  nearest  to  it  on 
either  side  shall  have  the  same  digit  in  the  same  place  of  figures. 

If  five  adjacent  light-houses  were  thus  numbered  :  361,  517,  243, 
876  and  182,  supposing  a  mistake  to  have  occurred  in  the  first  time 
of  counting  243,  and  that  it  had  been  reported  to  the  master  of  the 
vessel  as  253,  he  would  immediately,  on  looking  at  his  numerical 
list  of  light-houses,  perceive  that  a  mistake  had  been  made  in  the 
middle  figure,  because  in  any  general  arrangement,  the  number  253 
would  have  been  assigned  to  some  light-house  on  a  coast  very  dis- 
tant from  that  on  which  243  was  placed.  In  fact,  two  out  of  any 
three  figures  would  always  detect  the  error  of  the  third. 


46 

The  law  of  numbering  just  stated  is  sufficient  for  the  present  ob- 
ject. Probably  a  little  inquiry  might  produce  a  still  better  arrange- 
ment. 

Thus,  occupations  would  distinguish  every  light-house  from  all 
casual  lights,  and  their  number  would  identify  the  light  itself.  The 
whole  illuminating  power  would  be  always  employed,  undiminished 
by  the  interposition  of  colored  glass.  These  lights  would  be  more 
easily  visible  at  a  distance,  because  it  is  known  that  the  eye  per- 
ceives more  readily  a  faint  light  which  is  intermittent  than  an  equal 
light  which  is  continuous. 

OF   HARBOR   LIGHTS. 

The  same  principle  of  numerical  lights  is  equally  applicable  to 
light-houses  which  indicate  harbors.  Information,  however,  of  an- 
other kind,  is  often  requisite  for  vessels  about  to  enter  them.  It  is 
always  desirable  that  the  depth  of  water,  either  within  the  harbor 
or  on  the  bar,  should  be  known. 

This  may  be  effected  most  simply  by  allowing  the  occultations  of 
white  light  to  indicate  the  number  of  the  light-house,  and  instead  of 
having  a  long  interval  of  white  light  between  each  repetition,  let  a 
colored  glass  be  placed  before  the  light,  and  a  number  of  occulta- 
tions be  made  equal  to  the  number  of  feet  of  water  existing  at  the 
time. 

Thus  a  tidal-harbor  light-house  will  continually  repeat  its  own 
proper  number  in  white  light,  followed  by  the  number  of  feet  of 
water  on  the  bar  in  colored  light.  If  it  should  be  thought  desira- 
ble, it  would  be  easy  to  make  the  color  of  the  light  Hue  when  the 
tide  is  rising,  and  green  when  it  is  falling. 

The  mechanism  for  harbor  lights  need  not  be  complicated,  and  by 
means  of  a  float  might  be  made  entirely  self-acting.  The  weight 
necessary  for  making  the  occultations  might  even  be  wound  up  by 
the  float  itself. 

Another  great  advantage  of  a  float  is,  that  the  depth  of  water  in- 
dicated will  always  be  the  real  depth  at  the  time.  The  computed 
depth  often  differs  from  the  true  depth,  owing  to  the  influence  of 
storms,  and  other  accidental  causes. 

Some  additions  to  this  mechanism  would  enable  it  to  indicate  the 
depth  of  water  on  the  bar  by  day  as  well  as  by  night. 


47 

OP   FOG  SIGNALS. 

During  the  prevalence  of  fogs,  the  lights  which  ought  to  guide  the 
seaman  are  often  indistinctly  seen,  or  entirely  obscured,  until  he  has 
approached  too  near  the  danger  against  which  they  were  intended  to 
warn  him. 

In  cases  of  fog,  light-ships  and  light-houses  are  in  some  instances 
provided  with  gongs  and  bells,  which  are  then  kept  constantly 
sounding.  It  is  unfortunate  that  the  means  of  warning  the  seaman 
of  his  danger  should  extend  to  the  shortest  distance  when  that  dan- 
ger is  most  imminent.  The  lights  usually  employed  are  visible  at  a 
distance  from  six  to  thirty  miles  ;  but  the  sound  of  a  gong  or  bell  is 
heard  at  a  comparatively  very  small  distance. 

When  these  instruments  are  heard  they  merely  indicate  danger, 
but  not  its  exact  nature.  It  might  in  some  cases  be  of  great  impor- 
tance that  the  gong  or  bell  should  indicate  the  number  of  the  light- 
ship. This  could  be  accomplished  by  a  very  trifling  alteration  in 
the  mechanism.  Instead  of  striking  the  instrument  at  fixed  inter- 
vals, let  there  be  pauses  and  a  long  interval  between  the  number  of 
strokes  which  successively  represent  the  digits  of  the  number  of 
the  light-ship,  just  in  the  same  manner  as  has  been  proposed  for 
light-houses. 

A  light-house  or  light-ship  whose  number  is  243,  would  be  thus 
indicated  during  fogs  : 

(2  blows  on  gong,)  pause,  (4  blows  on  gong.)  pause,  (3  blows  on 
gong,)  long  interval. 

The  same  mechanism  which  caused  the  occultations  of  the  light, 
might  produce  the  blows  on  the  gong. 

The  preceding  explanations  are  sufficient  to  show  that  each  light- 
house or  light-ship,  by  continually  repeating  its  own  number,  might 
render  any  mistake  of  it  for  a  different  light  very  nearly  impossible. 
The  great  principle  on  which  the  system  rests,  is  to  give  numerical 
expression  to  each  light.  If  it  be  not  thought  necessary  to  apply  it  to 
every  light-house,  the  most  important  may  be  chosen  for  its  appli- 
cation. The  expense  of  the  alteration,  and  the  amount  of  danger 
incurred  by  a  mistake,  will  furnish  the  ground  of  decision  in  each 
individual  case. 

In  proposing,  however,  a  new  system  which  has  extensive  bear- 
ings on  other  questions  connected  with  the  safety  of  those  who 


48 

travel  on  the  waters,  it  is  desirable  that  a  general  and  comprehen- 
sive view  should  be  taken  of  such  of  its  applications  as  the  rapid  ad- 
vance in  mechanical  and  chemical  science  justify  us  in  supposing 
must  take  place  in  a  few  years. 

However  partially  the  system  may  be  adopted  at  first,  a  judicious 
foresight  into  its  probable  applications  may  enable  us,  without  any 
present  inconvenience,  to  accelerate  future  improvements,  and  to 
save  considerable  expense  on  their  adoption. 

The  following  suggestions  for  improvements  or  applications,  many 
of  which  are  perfectly  practicable  at  the  present  time,  are  offered 
for  the  consideration  of  those  who  may  be  called  upon  to  carry  out 
the  Numerical  System  of  Light-houses.  They  are  not  necessary  for 
the  success  of  the  simple  plan  which  has  been  already  described, 
but  may  be  adopted  or  rejected  without  any  interference  with  it. 

SUGGESTIONS  FOE  THE  IMPROVEMENT  OF  LIGHT-HOUSE  SIGNALS,  BUOYS,  &C. 

Telegraphic  communication  during  the  night  between  liglit-liouses  and 
ships  in  distress. 

Cases  occur  in  which  it  is  of  great  consequence  that  a  ship  should 
communicate  with  the  land  long  before  it  can  send  a  boat  ashore,  or 
enter  its  intended  port.  It  may  be  the  bearer  of  important  intelli- 
gence. It  may  convey  some  personage  whose  presence  is  essential 
for  some  great  object.  The  vessel  itself  may  be  in  distress.  The 
state  of  the  elements  may  render  it  impossible  to  send  for,  or  re- 
ceive, any  assistance  from  the  land  j  yet,  even  under  such  unfavorable 
circumstances,  if  directions  from  skilful  pilots  acquainted  with  the 
coast  could  be  conveyed  to  the  ship,  its  wreck  might,  perhaps,  be 
prevented  ;  or,  if  driven  on  shore,  having  been  directed  to  the  least 
unfavorable  spot,  its  crew  might  possibly  be  saved. 

Such  communications  might  easily  be  organized.  There  are 
already  existing  in  the  Royal  Navy  in  the  East  India  Company's  ser- 
vice, and  elsewhere,  large  dictionaries  of  numerical  signals.  These, 
it  is  true,  are  made  by  flags,  or  by  balls  ;  but  the  same  numbers 
may  be  expressed  by  the  occultations  of  lamps.  Any  number,  how- 
ever large,  may  be  expressed  by  making  the  number  of  occultations 
corresponding  to  the  first  or  highest  digit,  then  allowing  a  pause  j 
after  which  the  number  of  occultations  representing  the  second  digit, 
then  a  pause;  and  so  on,  always  observing  that,  after  the  unit's 
figure  has  been  expressed,  there  must  follow  a  long  interval. 


49 

The  plan  for  telegraphic  communication  would  be  thus  arranged  : 

1.  Light-house  repeating  its  own  number. 

2.  Ship  fires  a  gun,  and  hoists  a  light,  to  call  the  attention  of  the 
light-keeper. 

3.  Light-house  ceases  repeating  its  number,  and  becomes  a  steady 
light,  thus  informing  the  ship  that  it  is  observed. 

4.  Ship  having  prepared  its  message,  numerically  expresses  it  by 
the  occultations  of  its  own  lamp. 

5.  Light-house  repeats  the  message  of  ship,  in  order  to  show  that 
it  has  been  rightly  understood. 

G.  Light-house  now  repeats  its  own  number,  whilst  it  is  preparing 
the  answer. 

7.  Light-house  expresses  its  answer  by  occultations. 

8.  Ship  repeats  the  answer. 

This  interchange  of  question  and  answer  is  continued  as  long  as 
necessary,  during  which  the  light-house  repeats  its  own  number  pre- 
viously to  each  reply. 

Very  little  delay  will  occur,  for  these  questions  and  answers  will 
be  arranged  on  movable  disks,  which  may  be  placed  in  the  mechan- 
ism employed  for  occulting,  even  whilst  it  is  repeating  another  mes- 
sage. Many  such  disks,  each  containing  a  different  message,  may  be 
placed  in  the  machine  at  once,  and  on  touching  any  lever  the  light 
will  continue  repeating  the  corresponding  message. 

In  case  of  a  ship  in  distress,  for  instance,  requiring  an  anchor  of 
given  weight,  it  may  be  necessary  to  send  to  the  harbormaster  of 
the  adjacent  port  to  give  the  order,  and  to  ascertain  the  time  when 
it  can  reach  the  vessel.  During  this  interval,  the  light-house  will 
be  repeating  its  own  number. 

An  electric  telegraph  from  the  light-house  to  the  dwelling  of  the 
harbormaster  would  save  much  time,  and  in  some  cases  much 
damage. 

The  gun  fired  by  the  vessel  might  also  be  heard  by  the  harbor- 
master, and  his  attention  then  being  directed  to  the  telegraph  light- 
house, the  whole  time  might  be  saved.  If  even  his  own  house  was 
invisible  to  the  ship,  but  within  view  of  the  light-house,  he  might 
by  means  of  a  small  light  correspond  with  the  ship  through  the  in- 
tervention of  the  light-house,  repeating  the  signals  of  both  parties. 

Colored  shades  might,  if  thought  expedient,  be  used  for  different 
dictionaries  ;  or  an  entirely  independent  lanthorn  might  be  specially 
4 


50 

devoted  to  signals  ;  but  this  would  cause   additional  expense,   and 
seems  unnecessary. 

It  may  be  objected  to  this  plan,  that  it  would  mislead  .other  ves- 
sels on  first  coming  in  sight  of  the  light-house.  This  objection, 
however,  will  be  found  on  examination  to  be  invalid  ;  for  a  ship  on 
first  getting  sight  of  a  light-house  will  be  at  the  distance  of  many 
miles ;  and  as  all  telegraphic  messages  would  consist  of  more  than 
three  places  of  figures  the  ship  would  immediately  perceive  that 
the  light-house  was  acting  telegraphically,  and  on  turning  to  the  dic- 
tionary, would  even  become  acquainted  with  its  message.  Besides, 
in  the  course  of  every  three  minutes,  at  least,  the  light-house  would 
repeat  its  own  number.  Thus  the  ship  would  always  know  that  it 
was  in  the  presence  of  a  light-house  ;  and  if  its  reckoning  did  not 
enable  it  to  identify  the  light,  it  could  only  remain  in  doubt  during  a 
few  minutes. 

Telegraphic  signals  letiveen  ships  at  night. 

The  application  of  the  system  of  occupations  to  ships  at  sea  may 
not,  perhaps,  be  quite  so  easy  as  that  which  is  proposed  for  light- 
houses, but  no  objections  have  yet  occurred  which  appear  at  all  in- 
surmountable. 

The  question  of  the  position  of  the  occulted  light  or  lights  placed 
011  the  ship  must  be  settled  by  practical  men  after  due  consideration 
and  experiment.  It  may,  however,  be  suggested  that  a  light  hid 
by  a  mast  or  sail  may  yet  have  its  occultations  made  perfectly  appa- 
rent by  reflection  from  another  sail.  If  such  a  system  of  signals 
were  adopted,  fleets  might  sail  in  company  during  the  night,  each 
repeating  its  own  number,  and  any  orders  could  be  conveyed  to  any 
individual  ship. 

Specific  lights  have  already  been  employed  to  distinguish  sailing- 
vessels  from  steamers,  in  order  to  prevent  collision.  By  adopting 
the  system  of  occultations  to  one  or  more  of  the  lights  of  steamers, 
their  character  would  appear  more  distinctly,  and  at  greater  dis- 
tances. Perhaps,  indeed,  it  would  be  better  to  have  the  distinctive 
character  of  a  steam  vessel  indicated  by  a  continual  enlargement 
and  diminution  of  its  light,  'rather  than  by  an  occultation.  Two 
steamers  also  would  have  much  less  reason  for  approaching  each 
other,  because  they  could  hold  any  correspondence  by  signals.  They 


51 

might  also  by  the  same  means  convey  to  each  other  their  intended 
course  long  before  they  approach  each  other. 
• 

Of  a  universal  dictionary  of  signals. 

Whether  the  system  of  occupations  be  generally  adopted  or  not, 
numerical  dictionaries  of  signals  have  been  found  absolutely  neces- 
sary, and  have  long  been  in  use.  The  rapid  increase  both  of  ships 
and  of  steamers  renders  some  common  language  for  all  nations 
almost  a  matter  of  necessity. 

The  concurrence  between  adjacent  nations  in  numbering  their  re- 
spective light-houses  would  be  essential  if  any  numerical  system  is 
adopted  for  distinguishing  them.  Such  an  opportunity  ought  not  to 
be  lost  of  rendering  those  discussions  still  more  useful  by  attempting 
to  organize  a  plan  for  an  universal  system  of  numerical  signals.  The 
first  step  might,  perhaps,  be  that  each  nation  should  supply  all  ques- 
tions and  answers  that  ships  could  ever  require  for  their  safety  or 
convenience.  Out  of  these,  the  duplicates  being  omitted,  the  first- 
draught  of  the  naval  part  of  the  dictionary  might  be  formed.  This 
being  submitted  to  criticism  would  probably  itself  suggest  many  ad- 
ditions. 

The  questions  should  be  very  carefully  translated  into  the  lan- 
guages of  all  maratime  nations,  and  should  be  printed  in  columns  for 
each  language. 

A  dictionary  of  this  kind,  containing  about  five  thousand  terms,  in 
ten  European  languages,  was  published  in  1849,  by  M.  K.  P.  Ter 
Reehorst.  The  words  are  contained  on  about  two  hundred  double 
pages  ;  and  since  each  word,  of  which  there  are  usually  about  twenty- 
five  in  a  page,  is  numbered,  this  work  might  be  used  as  a  numerical 
telegraphic  dictionary. 

If  a  more  general  dictionary  were  undertaken,  other  considerations 
arise,  and  the  great  questions  relating  to  the  philosophy  of  language 
must  be  examined  with  reference  to  such  a  work.  It  will,  however, 
be  sufficiently  early  to  enter  on  that  subject  when  any  steps  are  se- 
riously taken  to  accomplish  so  desirable  an  object. 

The  continually  increasing  use  of  the  electric  telegraph  renders  an 
universal  language  still  more  desirable. 


52 


ON   THE   IDENTIFICATION    OF   A   LIGHT-HOUSE. 

A  case  has  been  more  than  once  suggested  to  the  author,  to  which 
it  may  be  desirable  to  advert  in  order  to  point  out  the  course  of  ex- 
periment which  may  lead  to  its  removal. 

At  certain  periods  of  the  year,  and  on  certain  coasts,  there  occur 
dense  fogs.  Under  these  circumstances  it  has  happened  that  a  vessel 
has,  on  a  partial  and  momentary  opening  in  the  fog,  insufficient  to 
show  more  than  a  single  occultation.  found  herself  almost  close  upon 
a  light-house.  In  such  a  case  there  is  neither  time  nor  opportunity 
to  ascertain  its  number. 

It  may  here  be  remarked,  that  the  assumed  danger  of  going  ashore 
is  so  imminent  that  it  is  not  necessary  to  know  the  number.  It  is 
sufficient  for  the  moment  to  know  that  there  is  a  light-house  in  a  cer- 
tain direction,  which  is  close  at  hand. 

It  must,  however,  be  admitted,  that  in  common  with  all  received 
systems  of  lights,  the  method  of  occupations  will  not  furnish  a  reme- 
dy. If  a  colored  light  is  already  employed  in  particular  localities  to 
meet  such  a  case,  it,  will  still  accomplish  the  purpose  when  occulta- 
tions  are  applied  to  it. 

The  danger,  although  rare,  ought,  however,  to  be  provided  against. 
The  following  remarks  are  suggested  to  assist  in  obtaining  that  object  : 
The  time  between  two  occupations  (usually  one  second)  might  be 
doubled  in  special  cases.  A  little  experience  would  enable  most  men 
to  recognise  the  fact  after  two  occupations.  If  such  light-houses  were 
placed  alternately  with  others,  no  light-house  would  be  mistaken  for 
either  of  its  adjacent  neighbors.  This  plan  might  be  partially  ex- 
tended, but  it  is  liable  to  objections. 

Another  view  maybe  taken.  Is  it  possible  to  give  a  specific  char- 
acter to  the  occultation  itself?  It  has  been  found  that  if  the  occult- 
ing cylinder  descend  rather  slowly  over  the  lamp,  and  then,  after  a 
very  short  pause,  rise  suddenly,  the  effect  is  best.  It  has  also  been 
observed,  when  an  accidental  defect  in  the  apparatus  caused  the  cyl- 
inder, after  suddenly  rising  up,  to  rebound,  and  again  to  obscure 
partially  the  lamp,  that  the  nature  of  the  occultation  was  peculiarly 
characteristic.  This  peculiarity  was  very  remarkable  up  to  a  certain 
distance,  after  which  it  became  lost.  Almost  any  form  of  peculiarity 
can  be  given  to  the  occultations,  by  giving  proper  forms  to  the  cams 


53 

which  govern  them.  The  fact  that  such  peculiarities  are  not  seen 
until  the  ship  has  approached  within  certain  distances,  does  not  ap- 
pear to  present  a  material  difficulty,  and  may  even  prove  an  advantage. 

It  would  seem,  then,  to  be  desirable  to  institute  a  series  of  experi- 
ments to  determine  the  following  questions  :  Can  the  occultations  of 
a  lamp,  in  which  the  rapid  reappearance  of  the  light  occurs  from  the 
falling  dotvn  of  the  shade,  be  distinguished  from  those  in  which  it  oc- 
curs in  consequence  of  the  rapid  rising  up  of  the  shade  ?  and,  if  sol  at 
what  distance  ?  In  some  cases  the  shades  might  move  from  right  to 
left,  and  in  the  reverse  direction.  What  peculiarities  in  occultations 
can  be  seen  at  the  greatest  distances  ? 

Amongst  the  experiments  still  required,  may  be  mentioned  the  loss 
of  light  resulting  from  the  interposition  of  colored  glasses,  and  also 
the  proportion  of  light  lost  by  sacrificing  given  portions  of  various 
parts  of  the  optical  apparatus  used  for  concentrating  it.  This  is  ne- 
cessary in  order  to  enable  us  to  judge  what  portion  may  be  most 
economically  sacrificed  in  case  the  space  might  be  required  for  other 
purposes. 

The  dangers  arising  from  fogs  are  of  such  an  extent  that  all  the 
resources  of  science  ought  to  be  called  in  to  remove  them. 

Voltaic  light  can  scarcely  be  depended  upon,  except  under  con- 
tinual superintendence  ;  it  would  therefore  be  expensive.  If,  how- 
ever, any  intense  light  can  be  found  capable  of  penetrating  dense 
fogs,  it  might,  during  their  continuance,  be  good  economy  to  employ 
it  even  at  considerable  expense. 

Perhaps  the  ordinary  light-house  lamps  might  be  supplied  with 
oxygen  during  fogs  ;  its  expenditure  being  regulated  by  the  obscurity 
to  be  penetrated. 

Possibly,  portions  of  phosphorus  might  be  burnt  in  oxygen,  and 
the  light-house  would  then  express  its  number  by  a  series  of  flashes, 
and  of  pauses  between  them.  The  new  form  which  that  body  is  now 
known  to  assume  might  render  its  application  to  this  purpose  free 
from  danger. 

ON   SOUNDS   USED   FOR   SIGNALS. 

Both  gongs  and  bells  are  employed  as  substitutes  for  lights  during 
fogs.  I  am  not  aware  of  any  series  of  experiments  on  the  distances 
at  which  sounds  of  various  kinds  can  be  heard.  In  a  question  on  which 


54 

so  much  property  and  so  many  lives  depend,  it  is  surely  important  to 
be  well  informed.  The  only  resource  is  experiment.  It  may  be  re- 
marked that  the  low  notes  of  the  gong  might  be  confounded  with 
those  of  the  roll  of  waves  breaking  on  the  shore,  whilst  the  shrill 
whistle  of  the  steam  engine  will  find  a  rival  in  the  wind  whistling 
through  the  rigging.  The  trumpet  and  the  new  and  still  more  pow- 
erful instrument  at  the  recent  exposition  ought  also  to  be  compared. 

Again,  although  some  of  these  may  be  heard  at  greater  distances 
in  the  open  air,  some  may  be  more  easily  adapted  to  have  their 
sound  concentrated  and  directed,  when  placed  in  the  focus  of  a  para- 
bolic mirror,  or,  perhaps,  at  the  end  of  a  long  tube. 

Sound  is  transmitted  to  considerable  distances  through  water,  and 
it  has  been  suggested  that  this  might  be  used  in  case  of  fogs.  But  it 
seems  probable  that  sound  would  be  much  interrupted  in  its  progress, 
from  the  constant  motion  of  the  waves;  and  if  it  were  transmitted  at 
a  considerable  depth,  it  might  be  difficult  for  a  vessel  to  send  down 
an  apparatus  to  render  it  sensible. 

Experiments  should  be  made  on  the  distance  at  which  sounds  can 
he  heard  under  water  in  various  circumstances  of  its  motion. 

If,  during  storms,  the  surface  only  is  agitated,  it  might  be  possi- 
ble to  transmit  sounds  in  the  still  water  near  the  bottom  to  consider- 
able distances.  Thus  channels  might  be  traversed  by  telegraphic 
communications  with  a  less  costly  apparatus  than  that  of  the  electric- 
wire.  It  ought  also  to  be  ascertained  whether  the  forms  of  the 
instruments  struck  would  enable  them  to  project  their  sounds  in 
particular  directions.  Gongs,  bells,  and  the  firing  of  cannon  under 
water,  are  among  the  sounds  to  be  tried. 

Whatever  may  be  the  sound  audible  at  the  greatest  distance,  it 
will  be  necessary  to  ascertain  what  are  the  best  means  of  producing 
it  in  greatest  intensity — whether  by  one  large  instrument,  or  by 
many  small  ones.  It  seems  probable  that  some  combination  of  dis- 
cordant sounds  may  be  most  effective,  because  it  seems  to  be  a  law 
of  our  nature  that  contrasts  produce  stronger  impressions  than  uni- 
formity. There  is  one  form  of  sound  the  most  disagreeable  with 
Avhich  we  are  acquainted;  it  is  said  "to  set  the  teeth  on  edge." 
What  is  the  cause  of  this,  and  does  that  highly  obnoxious  sound 
penetrate  further  than  others?  If  it  penetrates  as  far  as  others,  it 
will  certainly  be  the  earliest  to  be  noticed. 


55 


LIGHTS   ON  BUOYS. 

The  time  is  probably  not  remote  when  lights  will  be  placed  on 
floating  buoys,  for  the  purpose  of  pointing  out  isolated  dangers — as 
sunken  rocks,  shoals,  &c.,  on  which  light-houses  cannot  be  placed, 
or  where  the  great  expense  may  prevent  them  from  being  built. 
They  may  also  be  useful  to  indicate  the  channels  leading  to  some  few 
ports  of  very  great  resort,  in  order  to  render  the  approach  of  vessels 
possible  during  the  night. 

The  first  difficulty  in  placing  lights  on  buoys  arises  from  the  neces- 
sity of  trimming  the  lamps,  and  of  supplying  them  with  fresh  oil. 
Galvanic  processes  seem  to  present  a  similar  difficulty.  The  chemical 
discoveries  of  recent  times,  however,  offer  some  hope  of  removing  it. 
By  the  destructive  distillation  of  peat,  of  coal,  and  of  shale,  as  well 
as  by  other  methods,  a  variety  of  combinations  of  hydrogen  and  car- 
bon have  been  obtained.  Some  of  these  only  remain  liquid  under  a 
pressure  of  two  or  three  atmospheres.  They  possess  considerable 
illuminating  power  ;  and  by  confining  them  in  a  close  vessel,  and 
allowing  a  very  small  aperture  for  their  escape  in  the  state  of  gas,  a 
jet  of  flame  may  be  produced,  of  uniform  magnitude,  and  without 
the  use  of  a  wick,  until  the  last  drop  of  fluid  has  evaporated.  If 
such  a  fluid  could  be  produced  at  a  moderate  price,  a  quantity  might 
be  enclosed  within  the  buoy,  sufficient  to  last  several  weeks,  if  not 
months. 

Such  a  light  would  burn  without  the  necessity  of  trimming,  but  it 
would  require  mechanism  to  light  it  each  evening,  and  to  put  it  out 
each  morning. 

Such  mechanism  already  exists  in  many  of  our  public  clocks.  If  it 
is  thought  desirable,  too,  that  it  should  occult,  so  as  to  indicate  its 
number,  the  plan  already  described  might  be  applied.  Thus  the 
buoy  would  contain  two  pieces  of  mechanism.  The  only  remaining 
difficulty  would  be  the  necessity  of  visiting  the  light  frequently  in 
order  to  wind  up  the  two  instruments.  This  might  probably  be  re- 
moved by  having  within  the  buoy  a  heavy  pendulum,  or  perhaps  two 
such,  swinging  at  right-angles  to  each  other.  If  the  perpendicular 
motion  of  the  buoy  could  be  secured,  then  the  winding  up  pendulums 
must  be  maintained  horizontally  by  means  of  a  powerful  spring. 
These,  by  the  action  of  the  waves,  would  be  continually  winding  up 
the  springs  which  drive  the  mechanisms.  This  might  be  so  arranged 
that  it  would  never  over-wind  them. 


56 

Spirits  of  turpentine,  benzole,  and  several  other  compounds, 
assume  a  gaseous  state  at  very  low  temperature.  If  the  end  of  a 
tolerably  thick  rod  of  metal  is  heated  by  the  flame  of  the  lamp,  and 
the  other  end  conducts  the  heat  to  the  bottom  of  the  fluid,  it  is  suffi- 
cient to  produce  a  continuous  stream  of  gas  to  supply  the  burner 
until  the  last  drop  of  the  fluid  is  exhausted.  Lamps  constructed  on 
this  principle  have,  under  various  names,  been  in  use  for  several 
years.  If  the  fluid  were  sufficiently  cheap,  one  of  these  movements 
might  be  dispensed  with,  by  allowing  the  light  to  burn  constantly 
during  the  day  as  well  as  the  night. 

New  forms  would  be  required  for  such  buoys.  Probably  a  columnar 
form,  weighted  at  the  bottom,  might  give  a  steadier  light  amid  the 
fluctuations  caused  by  the  waves.  These  buoys  should  be  attached 
to  their  moorings  by  rings  fixed  at  the  centre  of  resistance. 

OF   THE   MECHANISM   NECESSARY   FOR   OCCULTING    LIGHTS. 

The  period  of  time  occupied  by  any  occulting  light  in  making  a 
signal  is  so  short  that  great  accuracy  in  the  wheel-work  is  not  neces- 
sary. In  light-houses  the  moving  power  may  be  a  heavy  weight 
driving  a  train  of  wheels.  This  must  terminate  in  a  governor,  which 
presses  by  springs  against  the  inner  side  of  a  hollow  cylinder. 

When  the  length  of  the  time  necessary  to  indicate  the  number  of 
the  light-house  is  known,  the  governor  must  be  so  adjusted  that 
some  one  axis  shall  revolve  in  the  given  time.  A  cam-wheel  must 
be  fixed  on  this  axis,  having  its  cams  and  blank  spaces  so  arranged 
as  to  lift  up  the  tail  of  a  lever  carrying  the  occulting  cylinder  at  the 
proper  intervals  of  time.  Each  tooth  of  the  cam-wheel  will  cause 
an  occultation  of  the  lamp  by  the  cylinder,  which  is  instantly  drawn 
back  by  a  spring. 

It  is  obvious  that  an  axis  might  be  used  which  moves  round  in  the 
course  of  two,  three,  or  more  cycles.  In  this  case  the  same  system 
of  cams  would  be  repeated  an  equal  number  of  times  in  the  circum- 
ference of  the  cam-wheel.  This  plan  is  sufficient  for  light-houses 
which  are  not  intended  for  signal  stations  also. 

When  signals  are  to  be  used,  it  is  better  to  have  a  single  cam.  on 
an  axis  which  revolves  once  in  the  time  which  elapses  from  the  end 
of  one  occultation  to  the  end  of  the  next.  The  effect  of  this  cam 
will  be,  by  acting  upon  a  forked  lever,  to  lift  up  the  occulting  cylin- 
der. If  nothing  retain  it  in  that  position,  the  action  of  the  spring  on 


57 

the  lever  will  cause  it  to  descend,  and  the  cylinder,  acted  on  by 
gravity,  will  instantly  follow.  But  if  an  arm  is  interposed  which 
retains  the  cylinder,  then  the  forked  lever  alone  will  be  pulled  back 
by  its  spring,  and  the  occulting  cylinder  will  remain  suspended  until 
the  next  turn  of  the  cam-wheel. 

The  suspending  arm  which  was  interposed  must  itself  be  governed 
by  a  cam-wheel,  expressing  the  number  of  the  light-house. 

When  a  signal  is  to  be  made,  an  adjustable  cam-wheel  is  to  be  set 
to  the  proposed  signal,  and  is  to  be  fixed  upon  the  axis  carrying  the 
constant  number  of  the  light-house.  When  the  proper  time  arrives 
for  making  the  signal,  it  is  only  necessary  to  shift  the  axis,  so  that 
the  adjustable  cam-wheel  shall  be  moved  into  the  place  occupied  by 
the  fixed  cam-wheel.  The  signal  will  now  be  made  and  repeated  as 
often  as  required,  after  which  the  original  position  of  the  constant 
cam-wheel  must  be  restored.  It  is  clear  that  any  number  of  adjust- 
ing cam-wheels  might  be  prepared  for  signals,  and  put  upon  the  axis 
at  once,  so  that  a  series  of  different  signals  might  be  made  in  a  very 
short  time. 

Lights  to  mark  the  depth  of  water  must  have  a  heavy  float  con- 
nected with  them,  which  at  every  foot  of  its  rise  or  fall,  must  alter 
the  number  of  occultations  made  by  the  colored  light.  It  must,  also, 
at  the  turn  of  the  tide  change  the  color  of  the  light,  It  is  sufficient 
for  the  present  purpose  to  observe  that  the  mechanism  similar  to  that 
by  which  a  clock  strikes  different  hours,  might  be  employed  for  this 
purpose. 

The  well  in  which  the  float  is  placed  ought  to  be  open  to  the  tide 
by  several  small  apertures  ;  this  would  render  the  rise  or  fall  of  the 
float  more  uniform. 

Telescopes  are  used  for  observing  light-houses.  They  have  a 
small  magnifying  power,  but  a  large  aperture.  It  is  important  that 
they  should  be  as  short  as  possible  for  taking  in  a  given  visual  angle. 
Possibly,  those  constructed  with  a  lens  of  rock-crystal  might  be  em- 
ployed with  advantage,  but  upon  this  subject,  also,  experiment  must 
be  made. 


58 


PARIS,  July  29,  1851. 

SIR  :  The  letter  which  you  have  done  me  the  honor  to  address  to 
me  under  date  of  27th  of  May  last,  only  reached  me  on  the  5th 
instant,  and  unfortunately  at  the  very  moment  of  my  departure  for 
London,  so  that  I  was  compelled  to  defer  replying  to  it  until  my 
return  to  Paris. 

I  still  belong  to  our  light-house  commission,  but  simply  as  a  mem- 
ber having  a  deliberative  voice.  I  obtained,  some  five  years  since, 
permission  to  retire  from  active  service  in  consequence  of  declining 
health,  and  was  replaced  in  the  double  capacity  of  secretary  to  the 
commission  and  inspector  of  light-houses,  by  my  fellow-laborer  of 
long-standing,  M.  L.  Reynaud,  engineer-in-chief,  professor  of  archi- 
tecture in  the  Polytechnic  school,  and  in  the  school  of  bridges  and 
roads.  (Ponts  et  Chaussees.) 

Consequently  your  letter  should  have  been  addressed  to  Mr.  Rey- 
uaud,  and  you  had  better  place  yourself  in  relations  with  him  for  all 
information  concerning  our  light-houses  ;  information  which  he  is 
now  more  able  to  furnish  than  myself. 

I  have,  therefore,  thought  it  best  to  return  to  the  legation  of  the 
United  States  the  documents  transmitted  through  it  from  yourself, 
with  a  request  that  they  may  be  addressed  to  our  minister  of  public 
works.  This  high  functionary,  I  am  well  assured,  will  most  cordially 
call  the  attention  of  M.  Reynaud  to  the  wishes  of  the  American 
commission  ;  and  you  may  rely  with  certainty  that  this  learned  and 
skilful  engineer  will  cooperate  zealously  in  promoting  the  success 
of  the  important  vocation  which  has  been  entrusted  to  you. 

Nevertheless,  in  order  to  fulfil,  so  far  as  I  can,  the  expectations 
of  the  eminent  persons  composing  your  Light-house  Board,  and  to 
obviate  as  much  as  possible  the  consequences  of  an  unavoidable 
delay,  which  I  regret  not  being  able  to  prevent,  I  will  endeavor  to 
answer  immediately  some  of  the  questions  you  have  addressed 
to  me. 

I  have  just  read  over  the  minutes  of  two  notes  which  I  had  the 
honor  to  transmit  to  you  under  the  dates  of  31st  of  December,  1845. 
and  13th  of  January,  1846  ;  and  I  can  but  reassert  the  declarations 
and  observations  contained  therein. 

Theoretically  considered,  the  relative  merits  of  the  two  systems  of 


59 

illuminating — catoptric  and  dioptric — seem  to  me  to  have  long  since 
been  clearly  established. 

In  a  practical  point  of  view,  the  question  does  not,  under  all  cir- 
cumstances, present  itself  in  so  simple  a  form.  There  are,  I  am 
aware,  certain  localities,  which,  in  consequence  of  the  difficulty  of 
communicating  with  them,  together  with  their  distances  from  work- 
shops, would  cause  some  hesitation  in  confiding  to  keepers  the  charge 
of  mechanical  apparatus,  when  so  isolated  from  the  means  of  repair- 
ing those  accidental  injuries  which  might  derange  the  whole  service 
of  seacoast  illumination. 

Nevertheless,  it  is  to  be  observed  : 

1.  Wherever  there  is  no  hesitation  in  using  the  revolving  appara- 
tus, there  should  be  none  in  the  application  of  mechanical  lamps  ; 
particularly  with  the  precaution  of  having  always  two  or  three  spare 
ones. 

2.  After  all,  the  difficulty  in  such  cases  resolves  itself  almost  in 
every  instance  into  a  question  of  expense,  which  is  a  minor  consider- 
ation where  an  important  light-house  is  in  question.    In  fact,  in  order 
to  secure  every  precaution,  it  may  be  sufficient  to  secure  for  the  chief 
keeper  a  mechanic,  provided  with  a  small  number  of  tools  and  other 
necessaries,  who  will  himself  repair  any  accident  which  may  happen, 
but  which  in  reality  very  rarely  occurs. 

3.  In  short,  communication  by  steam  in  the  United  States  is  now 
so  wonderfully  developed  that  no  point  in  its  immense  coast  can  well 
be  considered  as  isolated. 

As  regards  the  feasibility  of  converting  a  catoptric  light  in  full 
operation  into  a  dioptric  one,  it  is  a  question  for  special  consideration, 
requiring  in  its  solution  a  very  searching  examination  into  local  cir- 
cumstances, and  into  the  means  of  supplying  a  temporary  illumination 
during  the  progress  of  transformation.  If  it  be  determined  to  erect 
a  new  tower  near  the  old  one,  of  course  all  difficulties  are  removed. 
The  operation  becomes  a  more  delicate  one  if  the  new  apparatus  is 
to  replace  the  old  one  in  the,  same  edifice.  Nevertheless,  a  similar 
operation  has  been  very  successfully  effected  in  our  light-houses  of 
Cordouan,  Ushant,  Du  Tour,  and  Havre,  (2;)  also  in  the  English 
light-houses  of  Inchkeith  island,  the  Isle  of  May,  South  Foreland. 
Eddystone,  &c.,  &c. 

In  France  we  have  not  only  substituted  almost  entirely  the  catop- 
tric apparatus  of  our  old  light-houses  and  beacons  by  the  dioptric 


one,  but  we  purpose  in  a  short  time  to  renew  two  or  three  of  our 
oldest  lenticular  apparatus,  not  that  they  have  in  any  manner  dete- 
riorated, but  because  their  plan  of  construction  has  been  so  much 
improved  upon  by  the  skill  of  our  artisans  of  the  present  day. 

On  the  1st  of  January  of  this  year  the  illumination  of  the  coasts 
of  France  and  her  colonies  comprised  one  hundred  and  ninety-eight 
lights,  large  and  small,  out  of  which  one  hurdred  and  thirty-two  had 
the  lenticular  apparatus  ;  thirty-one  of  which  were  of  first  order,  six 
of  the  second,  eighteen  of  the  third,  and  seventy-three  of  the  fourth. 
The  increase  since  the  31st  of  December,  1845,  has  been,  in  lenticu- 
lar apparatus  twenty-one,  of  which  four  were  of  the  first  order,  three 
of  the  second,  and  fourteen  of  the  fourth. 

Our  seacoast  illumination  being  about  completed,  at  all  events  for 
the  coasts  of  France  and  Corsica,  \vill  receive  little  or  no  modifica- 
tions, so  far  as  the  lights  of  the  three  first  orders  are  concerned.  As 
to  the  small  movable  beacon  lights,  fixed  upon  scaffolding  at  the 
entrance  of  several  of  our  harbors,  they  continue  to  be  lighted  by 
small  reflectors. 

I  have  not  the  documents  necessary  to  enable  me  to  reply  to  your 
questions  concerning  the  foreign  lenticular  lights.  I  only  know  their 
numbers  to  be  already  considerable,  and  that  fresh  orders  have 
reached  our  artisans  from  Denmark,  Sweden,  England,  Spain,  and 
Italy. 

Some  lenticular  apparatus  have  been  made  in  England  by  Mr. 
Cookson.  of  Newcastle,  who  soon  renounced  a  manufacture  which  he 
doubtless  found  of  but  little  profit.  Two  lenticular  apparatus  of  the 
first  order,  one  English,  the  other  French,  are  now  displayed  at  the 
great  exhibition  in  London.  So  far  as  the  cutting  of  the  glass  is 
concerned,  I  conceive  them  to  be  of  equal  merit ;  but  in  whiteness, 
the  Birmingham  glass  cannot  stand  a  comparison  with  that  of  St. 
Gobain.  As  to  what  relates  to  the  organization  of  the  light-house 
service,  the  most  important  modification  since  my  retirement  appears 
to  me  to  have  been  the  applying  to  our  whole  seacoast  the  system  of 
administration  which  we  had  previously  tested  for  several  years  on 
the  coast  of  the  English  channel.  By  this  measure  all  the  light - 
keepers  have  been  placed  under  the  exclusive  direction  of  the  engi- 
neers, so  that  we  shall  have  no  longer  the  struggle  against  the  par- 
simonious tendencies  of  the  contractors. 

I  subjoin,  herewith,  two  documents,  drawn  up  and  published  by 
M.  L.  Reynaud  in  1848,  to  wit : 


61 

1.  New  directions  for  the  keeping  of  lenticular  lights. 

2.  A  schedule  of  charges  for  the  furnishing  of  oil  for  the  illumina- 
tion of  our  coasts. 

I  shall  close  here,  my  reply,  which  may  cover,  satisfactorily,  the 
principal  points  in  the  series  of  questions  you  have  presented.  More 
ample  information  will  doubtless  be  forwarded  to  you  by  M.  Rey- 
naud,  especially  upon  the  improvements  introduced  into  the  con- 
struction of  lenticular  apparatus,  with  their  lamps,  upon  the  present 
cost  of  these  apparatus,  and  upon  the  number  sent  from  Paris  to  for- 
eign countries. 

You  may  also  consult  with  advantage  two  works  published  by  Mr. 
A.  Stevenson  : 

1.  Account  of  Skerry vore  Light-house,  in  folio,   Edinburgh,  Adam 
and  Charles  Black— 1848. 

2.  Rudimentary  Treatise  on  Light-houses,  in  12mo. ;  London,  John 
Weale,  High  Holborn— 1850. 

While  regretting  that  my  present  position  has  not  enabled  me  to 
be  more  full  and  satisfactory.  I  can  but  congratulate  myself,  sir,  upon 
the  occasion  afforded  me  of  recalling  myself  to  your  kind  recollection, 
and  renewing  the  assurances  of  the  high  esteem  of  your  devoted 
servant,  LOR.  FRESNEL, 

Divisionary  Inspector  of  Bridges  and  Roads, 

and  Member  of  the  Light-house  Commission, 

No.  52  Rue  de  Lille,  d  Paris. 
Lieut.  THORNTON  A.  JENKINS,  U.  S.  N., 

Secretary  Light-house  Board,   Washington. 


LIGHT-HOUSE  COMMISSION, 

Paris,  July  23,  1851. 

Sm  :  I  have  the  honor,  herewith,  to  address  you  a  note  in  reply  to 
the  questions  contained  in  your  letter  of  27th  May  last,  which  only 
reached  me  on  the  Tth  of  the  present  month.  I  send  you  at  the  same 
time  a  collection  of  documents  (printed)  relating  to  the  light-house 
service,  also  some  specimens  of  wicks  and  glass  chimneys,  such  as  are 
now  in  use. 

I  regret  that  the  business  with  which  I  am  overwhelmed  on  the 
eve  of  a  tour  of  inspection,  involving  an  absence  from  Paris  of  three 
months,  will  not  allow  me  to  enter  more  into  detail  in  my  answers  ; 
but  I  know  that  my  very  honorable  predecessor,  Mr.  Fresnel,  has 
already  supplied  you  with  documents  on  this  subject,  and  that  your 
enlightened  and  perspicuous  mind  will  well  admit  of  conciseness. 


62 

You  will  find  me,  however,  very  ready  to  reply  to  all  calls  upon 
our  experience  which  you  may  do  me  the  honor  to  address  to  me. 
Be  pleased,  sir,  to  accept  the  expression  of  my  high  consideration, 

L.  REYNAUD, 

Engineer-in-chief.  Secretary  to  the  Light-house  Commission, 

charged  with  the  direction  of  the  service. 
To  Mr.  JENKINS, 

Lieut.  U.  8.  N.,  Secretary  Light-house  Board  of  the  U.  S. 


A  reply  to  the  questions  addressed  to  the  engineer -in-chief ,  secretary  to 
the  Light-house  Commission  of  France,  by  Mr.  T.  A.  Jenkins,  secre- 
tary of  the  Light-house  Board  of  the  United  States. 

Mr.  Jenkins,  secretary  of  the  Light-house  Board  of  the  United 
States,  has  done  me  the  honor  to  address  to  me,  in  the  name  of  this 
Commission,  several  questions  relative  to  the  light-house  service.  I 
will  reply  to  them  in  succession,  following  the  same  order  in  which 
they  have  been  put. 

1.  What  have  been  the  increase  and  improvements  in  the  seacoast 
illumination  of  France  since  the  year  1845? 

The  reply  to  this  question  is  shown  by  the  comparison  between 
the  annexed  list  of  light-houses  illuminated  on  the  1st  January,  1851, 
and  that  which  was  published  in  1845.  The  following  table  will 
exhibit  this  more  plainly  : 


Apparatus.                                         !  No 

in  1845.   ;   No.  in  1851. 

LIGHTS 

OF  FIRST  ORDER. 

31               *35 

4                  f2 

) 

3                   5 
1                   0 

13  '               16 

57                 66 
42                 40 

Reflector  

LIGHTS  OF  SECOND  ORDER. 

Reflector  

LIGHTS 

OF  THIRD  ORDER. 

LIGHTS  OF  FOURTH  ORDER  —  BEACONS. 

Reflectors  

The  lights  of  Algiers  and  the  colonies  are  not  comprised  in  this  table.  The  two  lights 
of  the  first  order  at  the  mouth  of  the  Canche  are  not  included  in  this  table.  It  is  expected 
that  they  will  be  lighted  in  a  few  months. 

t  These  two  apparatus  will,  in  all  probability,  be  replaced  in  1852  by  lenticular  apparatus. 


63 

2.  What  improvements   have   been  introduced  into  the    Carcel 
lamps  ;  and  are  other  lamps  used? 

According  to  the  annexed  statement  of  instructions,  published  in 
1848,  upon  the  service  of  lenticular  lights,  three  kinds  of  mechanical 
lamps  were  in  use  at  that  time  in  the  lighting  of  light-houses  of  the 
three  first  orders.  They  are  in  use  still.  Of  these,  the  Wagner 
lamp,  the  last  of  the  three  in  the  order  of  invention,  is  perhaps  the 
one  most  to  be  relied  upon  for  regular  use  ;  its  mechanism  is  very 
simple,  and  it  is  secured  with  all  necessary  solidity.  There  has  just 
been  made,  for  one  of  the  lights  of  the  first  order,  which  will  bo 
shortly  lighted  at  the  mouth  of  the  Canche,  a  lamp  with  four  concen- 
tric wicks,  placed  according  to  the  system  of  the  moderator  lamp. 
except  that  the  spiral  spring  is  replaced  by  a  weight  which  acts  on 
the  piston,  (see  description  of  the  moderator  lamp,  p.  8  of  the  in- 
structions upon  the  service  of  beacons.)  This  lamp — which  would 
be  less  expensive  than  the  preceding  ones,  and  more  easily  kept — 
has  given  very  good  results  in  the  many  trials  which  have  been  made 
in  the  light-house  workshops  ;  nevertheless  the  result  of  a  longer 
trial  will  be  waited  for  before  applying  it  to  other  light-houses. 

3.  What  oil  is  used? 

Colza  oil  is  used  in  the  light-house  service.  Numerous  experiments 
have  proved  that  this  oil  is  the  best  for  lighting  ;  it  is,  moreover,  at 
present  the  most  economical.  Some  years  since  the  contractors  for 
the  furnishing  of  oil  asked  authority  to  substitute  for  it  olive  oil,  for 
the  lights  of  Corsica,  on  account  of  the  difficulty  of  procuring  the  oil 
of  colza.  They  stated,  besides,  that  the  first  of  these  oils,  properly 
prepared,  was  eminently  suitable  for  lighting. 

Experiments  were  then  made  to  compare  the  two  oils.  Two  lamps 
of  the  first  order,  similarly  placed,  were  filled,  one  with  colza  oil,  the 
other  with  olive  oil ;  they  were  lighted,  and  the  flame  received,  as 
nearly  as  possible,  the  same  degree  of  adjustment.  Two  metallic 
screens,  each  pierced  with  an  opening  of  the  same  dimensions,  were 
placed  before  the  flames,  and  at  the  same  height,  and  the  rays  of 
light  passing  through  these  openings  were  measured.  This  experi- 
ment was  repeated  several  times,  and  it  established  that  the  light  of 
the  flame  from  the  oil  of  colza  was  represented  by  1.00  ;  that  of  the 
other  flame  had  for  its  mean  value  0.88. 

It  was  proved,  besides,  that  the  consumption  by  the  two  flames, 


64 

at  the  same  graduation,  was  represented,  for  the  colza  oil,  1.00  ; 
while  that  of  the  olive  oil  reached  1.137. 

The  authority  asked  for  was  refused. 

Other  experiments  were  made,  a  few  months  since,  on  a  mineral 
oil — the  oil  of  schiste.  They  established  that,  when  the  flame  was 
well  managed,  it  gave  a  light  notably  superior  to  that  which  is 
obtained  from  the  oil  of  colza ;  but  when  the  flame  was  agitated,  or 
the  lamp  did  not  perform  perfectly  well,  it  evolved  extremely  thick 
smoke,  which  quickly  darkened  the  apparatus.  It  would  be  neces- 
sary to  have  a  lamp  specially  adapted  to  the  burning  of  this  oil. 
These  experiments  will  be  followed  up,  and  they  may  perhaps  lead 
to  satisfactory  results ;  but  in  the  actual  state  of  things  the  oil  of 
schiste  cannot  be  applied  to  light-house  illumination. 

Some  trials  have  been  made  with  hydrogen  gas,  and  with  a  mixture 
of  hydrogen  and  oxygen,  and  they  have  given  good  results  as  to  the 
quantity  of  light  produced,  but  the  expense  would  be  greater ;  and, 
what  would  be  a  capital  defect,  less  certainty  in  the  continuance  of 
the  light. 

4.  To  what  tests  are  the  oils,  wicks,  and  chimneys  submitted? 

The  articles  8,  9,  10,  11,  and  12,  of  the  schedule  of  charges  rela- 
tive to  the  furnishing  of  colza  oil,  will  answer  the  first  part  of  this 
question. 

As  to  the  wicks  and  chimneys,  they  are  examined  to  see  if  those 
delivered  arc  conformable  to  the  model  deposited  in  the  central 
workshop  for  light-houses.  There  is  sent  with  this  note  specimens 
of  the  different  kinds  of  wicks  and  chimneys,  which,  after  numerous 
trials  have  been  definitely  adopted  for  the  service  of  lights. 

5.  At  what  periods  are  the  inspections  of  lights  made  ? 

The  light-houses  are  placed  in  charge  of  the  engineer  corps  of 
bridges  and  roads,  (ponts  et  chaussees.)  In  each  district  there  is  an 
engineer-in-chief  and  engineers ;  these  last  have  under  their  orders 
agents  who  have  the  title  of  conductors.  Each  light  is  placed  under 
the  immediate  superintendence  of  a  conductor,  who  visits  it  at  least 
once  a  month,  but  in  most  cases  oftener. 

The  engineer  never  remains  more  than  three  months  without 
visiting  the  lights  of  his  district,  and  the  engineer-in-chief  inspects 
those  of  his  department  at  least  once  a  year.  Finally,  the  engineer 
charged  with  the  direction  of  the  light-house  service  makes  each 
year  an  inspection,  which  embraces  one -third  of  the  sea  coast,  in 


order  that  he  may  examine  each  of  these  establishments  at  least 
once  during  the  three  years.  These  visits  are  made  by  day  and  by 
night.  Each  conductor  is  provided  with  keys  by  which  he  may 
enter  unawares,  even  into  the  lantern  itself,  in  order  to  ascertain  if 
the  light  be  attended  to  according  to  the  regulations.  The  port- 
officers  and  harbormasters  have  orders  to  transmit  to  the  engineers 
all  complaints  from  navigators,  upon  the  keeping  of  the  lights. 

6.  What  is  the  number  of  keepers  to  each  light  ? 

The  number  of  keepers  is  fixed  at  three  for  lights  of  the  first 
order,  and  two  for  lights  of  the  second  and  third  orders.  Beacon- 
lights  have  but  one  keeper  j  but  another  keeper  is  added  when 
these  establishments  are  placed  on  rocks  isolated  in  the  ocean,  or 
uninhabited  islands,  that  these  agents  may  have  by  turns  a  regular 
leave  of  absence,  without  exposing  the  service  to  suffer  therefrom. 
The  detailed  estimates  of  the  annual  expenses  of  illumination  will 
show  the  number  of  keepers  in  each  of  the  light-houses  in  France. 

7.  What  is  the  annual  expense  of  repairs  to  the  Carcel  lamp  ? 
The  detailed  estimates,  which  served  in  1838  as  the  basis  of  the 

contract  for  illuminating  the  light-houses  of  the  ocean  and  of  the 
Mediterranean,  had  valued  this  expense  at  seventy-five  francs  per 
year  for  the  lights  of  the  first  order,  at  sixty-five  francs  for  those  of 
the  second  order,  and  at  forty-eight  francs  for  those  of  the  third 
order.  This  valuation  was  too  large.  Thus,  in  1850,  the  expense 
incidental  to  this  object  for  twenty-eight  lights  of  the  first  order, 
four  of  the  second  order,  and  thirteen  of  the  third  order,  only 
reached  917.80  francs,  whilst  the  price  before  named  would  bring  it 
to  2,984  francs. 

In  order  to  answer  Mr.  Jenkins's  last  question,  I  add  to  this  note 
some  printed  documents  designated  as  follows  : 

Instructions  upon  the  organization  and  superintendence  of  the 
service  of  lights  and  beacons  — 1842. 

Schedule  of  charges  and  detailed  estimates  relative  to  the  furnish- 
ing of  the  oil  of  colza—  1848. 

Detailed  estimates  of  the  annual  expenses  of  the  service  of  light- 
houses and  beacons — 1848. 

Rules  for  the  keepers  of  lights  and  beacons — 1848. 

Two  government  circulars  (20th  and  28th  November,  1848)  upon 
the  new  organization  of  the  light-house  service. 

Instructions  for  the  service  of  lenticular  lights —  1848. 

Instructions  for  the  service  of  beacons — 1848. 
5 


66 

Circular  (20th  December,  1848)  of  the  engineer-in-chief,  charged 
with  the  service  of  lights. 

Light-keepers'  book. 

Description  of  the  light-houses  and  beacons  lighted  on  the  coasts 
of  France  on  the  1st  January,  1851. 

I  will  add  that,  since  1845,  the  construction  of  lenticular  appara- 
tus has  made  marked  progress,  and  that  the  use  of  curved  mirrors, 
to  transmit  to  the  horizon  the  rays  which  pass  above  or  below  the 
dioptric  drum,  are  abandoned  ;  these  rays  are  collected  by  catadiop- 
tric  prisms,  which  give  them  the  desired  direction  by  total  reflection. 

This  arrangement  produces  a  notable  economy  of  light,  and  is 
eminently  favorable  to  the  durability  of  the  apparatus. 

I  regret  to  be  obliged  to  give  so  concise  a  form  to  the  present 
note,  but  the  letter  of  Mr.  Jenkins  only  reached  me  a  few  days  since, 
although  it  was  dated  the  27th  of  May,  and  I  am  on  the  eve  of  my 
departure  for  an  inspection,  which  will  take  me  from  Paris  for  nearly 
three  months.  Yet  I  am  not  willing  to  defer  my  reply  until  my  re- 
turn, for  this  delay  would  seem  long,  and  might  occasion  doubts  of 
my  lively  desire  to  reply  to  the  honorable  appeal  of  the  Light-house 
Board  of  the  United  States.  I  hope,  moreover,  that  the  accompany- 
ing printed  documents  will  furnish  all  the  desirable  data  in  the  or- 
ganization of  the  light-house  service  of  France  ;  but  should  I  be 
mistaken,  I  pray  Mr.  Jenkins  to  designate  the  points  upon  which 
any  further  elucidation  may  appear  to  him  to  be  necessary.  I  will 
hasten  to  reply  to  such  inquiries,  happy  to  furnish  a  great  and  illus- 
trious nation  with  that  experience  which  has  been  acquired  by  long 
practice  and  conscientious  studies. 

I  pray  the  Light-house  Board  of  the  United  States  to  accept  the 
expression  of  my  sympathy  with  their  labors,  and  of  my  respectful 
devotion. 

L.  REYNAUD, 
Eng.  in  Chief,  Sec.  of  the  Light-house  Commission, 

charged  loitli  the  direction  of  the  service. 
PARIS.  July  23,  1851. 

P.  S.  I  add  to  the  documents  enumerated  in  the  present  note 
others  which  might  be  considered  of  some  use  : 

1st.  Drawing,  giving  the  arrangement  of  a  chimney,  surmounted 
by  its  regulator,  of  sheet  iron. 

2d.  Two  drawings  of  models  adopted  by  the  French  government 
for  the  building  of  beacons. 


6.7 

3d.  Directions  on  the  placing  of  lanterns  and  of  apparatus  for 
lenticular  beacons. 

There  have  been  no  written  instructions  for  the  establishment  of 
light-houses,  because  this  difficult  and  delicate  operation  is  always 
directed  by  one  of  the  conductors  attached  to  the  central  service. 


PARIS,  July  28,  1851. 

SIR  :  I  have  the  honor  to  acknowledge  the  receipt  of  your  es- 
teemed letter  of  the  29th  May  last,  and  the  valuable  documents 
which  accompanied  it. 

I  observe  with  great  pleasure  that  the  United  States  government 
favors  the  introduction  of  the  lens  system  of  lights,  and  that  a  regu- 
lar organization,  similar  to  that  which  we  have  in  France,  is  pro- 
posed. 

Such  an  administration,  composed  of  such  learned  and  able  men, 
cannot  fail  to  produce,  in  a  short  time,  great  improvements  in  the 
illumination  of  the  coast,  and  greatly  to  the  advantage  of  commerce 
and  navigation,  which  is  so  extensively  and  actively  carried  on  in 
the  United  States. 

You  will  find  herewith,  sir,  a  brief  account  of  the  different  im- 
provements which  I  have  introduced  into  the  lens  system  since  your 
visit  to  Paris  in  1846.  and  the  number  of  lenses  which  I  have  con- 
structed since  that  time. 

I  hope  that  the  occasion  may  present  itself  to  enable  you  to  judge, 
from  your  own  observation,  of  the  importance  and  value  of  these 
changes  ;  and  I  shall  employ  all  my  efforts  to  merit  the  approbation 
of  the  Light-house  Board,  and  of  yourself. 

I  have  the  honor  to  be,  with  great  respect,  your  obedient  servant, 

HENRY  LEPAUTE, 
Constructor  of  Le.ns  Apparatus.  No.  247  Rue  St.  Honorc,  Paris. 

To  Mr.  THORNTON  A.  JENKINS, 

Secretary  to  the  L.  H.  Board  of  the  United  States  of  America. 


68 

PARIS,  July  28,  1851. 

Note  upon  lens  apparatus,  and  upon  numerous  improvements  in  the  opti- 
cal and  mechanical  parts  of  them,  by  Henry  Lepaute,  constructor  of 
lenticular  apparatus,  No.  247  Rue  St.  Honors,  Paris,  France. 

The  constant  and  uninterrupted  study,  by  the  undersigned,  of  the 
construction  and  management  of  lens  lights,  has  enabled  him  to  in- 
troduce modifications  in  the  mechanical  lamps,  which  have  rendered 
their  repair  much  easier. 

Escapement  lamps,  upon  the  plan  of  Henry  Lepaute. 

As  some  inconvenience  has  resulted  from  the  manner  in  which  the 
escapements  were  attached  to  them,  their  form  has  been  changed, 
and  they  have  now  had  a  solidity  given  to  them  which  remedies  that 
defect. 

The  levers  which  bind  the  escapements  to  their  vertical  axes  were 
formerly  of  unequal  lengths,  from  which  it  frequently  resulted  that 
inattentive  keepers  sometimes  substituted  one  for  the  other,  thus 
producing  a  great  inequality  in  the  flow  of  the  oil.  Now,  however, 
by  a  new  arrangement  these  inconveniences  no  longer  exist,  and  it 
is  found  in  practice  that  the  management  of  it  is  greatly  facilitated. 
Notwithstanding  the  perfection  to  which  these  escapement  lamps 
have  reached,  and  the  great  attention  given  to  their  management,  I 
have,  under  the  direction  of  M.  Degrand,  under  engineer  to  the 
French  light-house  establishment,  constructed  a  new  lamp,  which 
seems  to  combine  all  the  qualities  of  simplicity,  durability,  and  facil- 
ity of  being  repaired,  which  ought  to  be  expected  in  this  descrip- 
tion of  apparatus,  to  make  them  as  near  as  possible  within  the  range 
of  the  comprehension  of  keepers  and  others  who  are  strangers  to 
mechanics. 

These  new  lamps  are  founded  on  the  system  vulgarly  called  the 
"  moderator."  Each  lamp  is  composed  of  an  iron  frame,  similar  to 
those  of  the  old  lamps,  supporting  a  cylindrical  reservoir,  in  which 
a  piston  is  placed  and  adjusted,  which  is  charged  with  regulators  of 
lead  in  sufficient  quantities  to  elevate  it  to  the  summit  of  the  burner; 
a  small  steel  cylinder,  upon  which  a  chain  is  wound,  serves  to  raise 
this  piston  by  means  of  a  crank,  and  in  this  ascending  motion,  the 
oil  with  which  the  reservoir  is  filled  above  the  piston  passes  beneath; 
the  action  of  the  piston  in  descending  causes  the  oil  then  to  rise  into 
the  burner,  and  the  overflow  to  fall  back  upon  the  same  piston. 


G9 

The  extreme  simplicity  of  this  lamp,  the  small  number  of  pieces 
of  which  it  is  composed  being  very  solid,  appears  well  adapted  to 
the  service  of  light-houses,  and  requires  that  the  keepers  should  pos- 
sess but  ordinary  ability  to  enable  them  to  manage  them. 

The  undersigned  takes  the  liberty,  then,  of  calling  the  attention 
of  the  Light-house  Commission  of  the  United  States  to  this  new  sys- 
tem. 

Numerous  improvements  of  detail  have  besides  been  added  to  the 
burners  and  to  the  means  of  carrying  off  the  smoke  ;  the  principal 
change  consists  in  a  new  ventilator,  in  which  a  damper  or  regulator 
is  adjusted,  which  by  these  means  does  not  rest  any  longer  upon  the 
glass  chimney  of  the  burner,  and  permits  the  exterior  current  of 
air,  which  is  introduced  by  the  lower  part  of  the  ventilator,  to  carry 
off  the  smoke  rapidly  from  the  burner  ;  the  strong  current  giving  a 
more  brilliant  flash,  and  preventing  the  action  of  the  exterior  cur- 
rents of  air  upon  the  top  of  the  regulator,  diminishes  strikingly  the 
breakage  of  the  glass  chimneys. 

In  1849,  the  undersigned  presented  to  the  French  industrial  ex- 
hibition, at  Paris,  a  lens  apparatus  of  the  first  order,  for  short 
eclipses,  upon  a  new  plan,  giving  in  the  space  of  two  minutes  a 
flash  of  sixty  seconds  duration,  followed  by  an  eclipse  of  twenty- 
five  seconds,  which  produced  a  brilliant  and  powerful  flash  of  ten 
seconds  duration,  which  was  succeeded  by  another  eclipse  of  twenty- 
four  seconds,  and  successfully  during  the  entire  night.  • 

This  apparatus  received  the  approval  of  the  Savans,  and  the  au- 
thor of  it  received  a  new  gold  medal.  It  had  been  constructed  by 
order  ol  Capt.  Stansbury  for  the  Carysfort  light-house,  and  was 
shipped  to  the  United  States  at  the  close  of  the  exhibition.  I  am 
ignorant  of  what  has  since  become  of  it,  and  its  value  has  not  yet 
been  paid  to  me. 

In  January,  1850,  the  undersigned  conceived  the  idea  of  a  new 
combination  of  catadioptric  apparatus  for  eclipses,  capable  of  pro- 
ducing flashes  equal  in  duration  to  the  eclipses,  and  arranged  in  a 
manner  to  show  each  five  seconds  a  brilliant  flash  of  five  seconds 
duration. 

The  new  character  of  these  lights  failed,  for  we  could  not  reach 
the  result  which  Mr.  Stevenson,  of  Scotland,  had  obtained  when  in 
giving  to  the  lens  apparatus,  constructed  up  to  that  time,  a  rotation 
so  rapid  that  rendered  the  flash  too  indistinct,  and  -would  not  permit 
the  navigator  to  see  it  for  a  sufficient  length  of  time. 


70 

A  lens  apparatus  was  ordered  of  the  undersigned,  by  Mr.  Lewis, 
ibr  the  Sand  Key  light,  and  its  execution  was  well  advanced,  when, 
in  the  month  of  March  last,  the  order  was  received  to  suspend  the 
further  execution  of  the  work  ;  not  having  received  any  new  in- 
structions, this  Avork  remains  unfinished. 

This  year  the  undersigned  is  about  arranging  a  new  mode  of  con- 
structing annular  lenses  for  eclipse  lights  :  that  modification,  which 
has  also  received  the  approbation  of  the  commissioner  of  lights  in 
France,  consists  in  the  new  division  of  the  lenses,  of  which  the  ele- 
ments divided  vertically  will  present  an  angle  of  four  to  five  de- 
grees, Avhich  will  greatly  increase  the  duration  of  the  flashes  and 
will  shorten  equally  that  of  the  eclipses. 

The  French  administration  is  about  to  order  from  the  undersigned 
an  apparatus  of  the  first  order  of  this  description  of  flashes  for 
every  minute,  to  renew  the  apparatus  of  the  light  of  Ailley,  near 
Dieppe,  and  another  of  the  same  order  for  eclipses  of  every  thirty 
seconds  for  the  light  of  the  Baleines,  near  La  Rochelle. 

In  these  new  apparatus  the  lenses  which  had  formerly  one  metre 
of  elevation  are  increased  to  1m. 30. 

Last  year  the  undersigned  commenced  the  construction  of  a  lens 
apparatus  of  the  first  order  for  the  Brazilian  government,  to  be 
placed  upon  Mount  St.  Paul,  near  Bahia.  The  apparatus  of  the 
first  order  of  total  eclipses  for  the  new  light,  is  of  a  combination 
entirely  new.  The  twelve  annular  lenses,  which  constituted  the 
dioptric  drum,  are  surmounted  by  twelve  catadioptric  panneJs,  trans- 
mitting to  the  horizon  the  flash  of  twelve  small  annular  lenses  placed 
in  the  interior  of  the  apparatus,  which  augment  and  prolong  strik- 
ingly the  flash  of  the  lenses. 

Above  the  dioptric  drum  are  placed  four  fractions  of  prisms, 
which,  turning  with  the  lenses,  add  also  their  power. 

In  this  apparatus  the  entire  optical  part  is  revolving,  and  there  is 
no  fixed  light  during  the  eclipse  ;  for  it  seemed  to  the  undersigned 
that  in  consequence  of  the  length  of  the  flashes  there  would  be  the 
advantage  of  rendering  the  eclipse  total,  while  the  flash  of  the  fixed 
light  of  revolving  apparatus  could  not  in  any  case  be  seen  so  far  as 
the  flash  of  the  lenses  ;  and  besides,  it  seemed  better  to  increase  the 
intensity  of  that  flash  and  increase  the  duration,  by  rendering  the 
eclipse  total.  That  combination  is  generally  preferred  by  the 
officers  of  the  navy,  to  whom  the  undersigned  submitted  his  plan 
before  putting  it  into  execution. 


71 

The  result  of  these  modifications  is,  that  the  revolving  apparatus 
of  the  second  order  would  equal  the  power  of  the  old  lens  apparatus 
of  eclipse  of  the  first  order,  and  naturally  produce  a  great  economy 
in  the  acquisition  of  equality  of  light. 

The  difficult  construction  of  these  new  apparatus  renders  the 
diminution  of  price  impossible,  and  the  undersigned  refers  for  their 
value  to  the  tariff  furnished  in  1845. 

HENRY  LEPAUTE, 
Constructor  of  lens  apparatus, 

No.  257  Rue  St.  Honor  e,  Paris. 


PARIS,  August  10,  1851. 

SIR:  I  had  the  honor  to  receive  your  letter  of  the  29th  May  from 
Washington,  on  my  return  to  Paris,  and  hasten  to  transmit  through 
your  legation,  agreeably  to  your  request,  numerous  documents  which 
will  serve  as  replies  to  the  questions  which  you  have  been  pleased  to 
address  me. 

I  have  the  honor  to  be,  sir,  your  very  obedient  servant. 

T.  LETOURNEAU. 
Lieut.  T.  A.  JENKINS,  U.  S.  N., 

Secretary  to  Light-house  Board,   Washington. 


NOTE  UPON  LENS  APPARATUS. 

IMPROVEMENTS  IN  THE  OPTICAL  AND  MECHANICAL  PARTS  OP  THE  APPARATUS. 

Considerable  improvements  have  been  introduced,  or  are  about  to 
be,  in  the  combination  and  composition  of  lens  lights.  I  will  treat  of 
them  here  in  a  general  way,  accompanied  by  a  brief  description. 

Although  the  most  of  these  improvements  are  due  to  my  researches, 
allow  me,  for  the  moment,  to  forget  the  duty  which  under  all  other 
circumstances  modesty  would  impose  upon  me,  and  attach  to  each  of 
them  the  name  of  the  author. 

Holophotal  apparatus,  by  Mr.  Stevenson. 

This  new  combination  converts  the  catadioptric  zones  into  annular 
zones,  thus  serving  to  extend  the  lenses  of  the  centre  the  total  height 
of  the  optical  part  of  these  lenses  which  is  contained  between  No.  G 


72 

of  the  zones  of  the  upper  and  the  No.  10  of  the  lower  part.  That 
combination  is  only  applicable  to  revolving  lights,  called  flashing, 
every  minute  or  every  half  minute  in  all  the  different  orders. 

In  taking  for  a  basis  of  prices  those  indicated  in  our  notices  of 
these  apparatus,  in  so  far  as  relates  to  the  frame  and  the  optical  por- 
tions, it  will  be  ten  per  cent,  more  expensive. 

Neiv  combination  in  the  lenses  of  the  drum  in  the  apparatus  of  short 
eclipses,  by  T.  Letourneau. 

This  arrangement  consists  in  replacing  the  lenses  of  vertical  ele- 
ments upon  an  exterior  frame,  making  its  revolution  around  a  drum 
of  a  fixed  light  by  a  system  of  fixed  light  lenses  and  annular  intercal- 
ary ones  between  them;  the  light  will  remain  in  appearance  other- 
wise the  same;  that  new  made  presents  a  useful  simplicity,  and  a 
striking  economy  in  the  cost  of  the  optical  parts. 

Combinations  common  to  apparatus  for  revolving  lights,  either  for  flashes 
for  every  minute,  half  minute,  or  for  short  eclipses,  by  T.  Letourneau. 

At  the  same  time  that  Mr.  Stevenson  made  his  researches  upon  his 
new  holophotal  lenses,  the  thought  of  increasing  the  intensity  of  the 
flashes  occupied  my  attention  also.  I  have  constructed  an  apparatus 
in  which  I  have  applied  before  these  catadioptric  zones,  the  same 
lenses  of  cylindrical  elements  which  I  reduced  to  the  apparatus  for 
short  eclipses,  (the  emergence  of  the  light  which  is  produced  by 
these  catadioptric  prisms  is,  as  is  well  known,  the  same  as  in  the 
fixed  light  drum;)  thus  placing  in  the  prolongation  above  and  below 
the  central  annular  lenses,  the  lenses  of  prisms  converging  horizon- 
tally. I  have  obtained  in  the  same  point  the  coincidence  of  the 
flashes  of  the  crown  lenses. 

Thus  composed,  this  apparatus  is  found  to  be  materially  increased 
in  value,  proportionally  to  the  number  of  supplementary  lenses  of 
which  it  is  composed;  but  the  placing,  so  far  as  relates  to  the  frame, 
does  not  exceed  the  small  increase  of  1,500  francs,  and  the  solidity  of 
the  system  presents  better  assurance  of  durability  and  of  regularity 
than  those  apparatus  of  the  same  kind  ordinarily. 

Annular  lenses  to  prolong  the  flashes  in  revolting  lights,  (Administration 

Francaise.) 

The  lenses  are  divided  into  two  parts,  and  by  their  centre  of  figure 
upon  the  height;  placed  in  a  manner  to  form  an  angle  of  some  degrees, 


73 

the  duration  of  the  flashes  increases  proportionally  to  that  inclination, 
but  at  the  expense  of  its  intensity.  That  combination  of  lenses  gives 
place  to  an  increase  of  ten  per  cent,  upon  the  cost  of  the  frame  and 
lenses. 

The  same  lenses  for  the  duration  of  the  flashes,  by  T.  Letourneau. 

Encountering  considerable  difficulty  in  the  construction  of  the  ex- 
isting frames  (the  preceding  system,  however  much  it  may  be  neces- 
sary to  regulate  the  uprights  to  the  demands  of  the  bed  of  the  frame,) 
in  place  of  dividing  horizontally  the  lenses,  I  divide  them  vertically; 
the  result  is  absolutely  the  same.  This  combination  of  lenses  gives 
an  increase  of  ten  per  cent,  for  each  lens. 

Revolving  lights  with  alternating  movement,  by  W.   Wilkins  and  T.  Le- 
tourneau. 

In  a  large  number  of  lights,  a  small  angle  of  the  horizon  is  only 
required  to  be  illuminated;  and  if  we  can,  in  a  fixed  light,  propor 
tion  the  number  of  lenses  of  the  drum  to  the  field  of  the  illumination 
required;  it  is  riot  the  same  in  revolving  lights,  as  the  drum  ought 
to  be  complete.  Having  been  solicited  by  many  orders  which  have- 
been  addressed  to  us.  treating  of  this  subject,  we  have  searched  for 
the  means  by  which  to  realize — 

1st.  The  advantage  sufficiently  striking  in  economy  which  would 
result  from  the  suppression  of  several  lenses. 

2d.  That  which  is  not  less  important  in  utility  by  the  means  of 
reflectors,  of  the  light  directed  from  the  land  side.  An  alternating 
movable  machine,  whatever  the  special  disposition  of  the  frame,  in- 
sures to  us  a  movement  very  regular  of  going  and  coming,  which 
circumscribes  the  march  of  the  revolving  lenses  in  an  eighth  or 
sixteenth  of  revolution. 

Glass  reflectors,  by  T.  Letourneau. 

For  the  old  metallic  reflectors,  the  inconveniences  of  which  arc 
appreciated,  I  substitute  reflectors  of  mirror  glass  (silvered.)  These 
new  reflectors  are  placed  at  a  distance  from  the  lamp,  which  varies 
with  the  horizontal  amplitude,  following  the  number  of  suppressed 
pannels,  and  of  the  distance  of  the  focus  from  0.307  to  the  back  of 
the  reflector  against  the  interior  side  of  the  lantern.  Let  us  conceive 
that  the  position  the  most  favorable  to  place  the  reflectors  is  the 
farthest  from  the  focus,  since  the  divergence  is  least  sensible. 


74 

Improvements  of  detail  in  construction  of  frames,    table  for  service, 
changing  the  lamps,  &c. ,  by  T.  Letourneau. 

One  of  the  greatest  difficulties  which  presents  itself  in  mounting 
a  first  order  lens  apparatus  in  its  tower  is  the  placing  the  table  of 
service,  which  up  to  this  time  is  made  of  a  single  piece.  I  have 
divided  them  in  the  lights  which  I  have  fitted  up  in  four  pieces, 
assembled  by  screws  and  nuts;  an  opening  arranged  under  the  stair 
allows  the  keeper  of  the  watch  to  place  alone  and  instantly  the  extra 
lamp.  These  arrangements  increase  the  price  of  the  frame  three 
per  cent. 

OLD    SYSTEMS. 

Floating  lights,  jixed  and  revolving,  with  Jens  apparatus,  l>y  T.  Letour- 
neau. 

The  floating  lights  at  present  in  use  are  composed  of  a  greater  or 
less  number  of  metallic  parabolic  reflectors,  adjusted  around  the 
masts  of  the  vessels  upon  Avhich  they  are  placed.  They  are  divided 
into  fixed  lights,  and  varied  by  flashes.  Besides  the  inconvenience 
due  to  the  multiplication  of  lamps,  there  is  not  a  sufficient  quantity 
of  light  produced  by  this  apparatus. 

NEW    SYSTEMS. 

The  new  floating  lights  are,  in  the  first  place,  of  four  refracting 
apparatus  for  fixed  lights,  embracing  an  angle  of  212  degrees.  Sec- 
ondly, of  spherical  reflectors,  making  for  the  optical  part  the  same 
focus  which  it  should  have  with  the  horizontal  amplitude  of  148  de- 
grees. These  apparatus  represent  very  nearly  a  weight  equal  to 
that  of  eight  reflectors  which  they  replace,  and  an  illumination  each 
by  a  lamp  consuming  0.045  grammes  per  hour. 

They  are  placed  in  suspension,  equidistant  from  each  other,  and 
in  whatever  manner,  always  directed  to  the  horizon,  and  whatever 
point  occupied  by  the  observer,  a  light  greatly  increased. 

The  prices  of  these  apparatus  are  fixed  for  the  set  of  four  optical 
parts,  reflectors  and  lamps,  4,800  francs.  For  the  lantern  3,000 
francs.  In  general  the  old  lanterns  may  be  used  for  new  apparatus. 

Revolving  machinery  for  floating  lights,  by  T.  Letourneau. 

As  much  from  communicated  as  personal  observation,  I  have  been 
convinced  of  the  inconveniences  arising  from  the  placing  of  rollers 


75 

between  plane  parallel  surfaces,  as  very  little  time  suffices  for  them  to 
make  a  succession  of  haclmres  or  indentations  sufficiently  marked  to 
change  the  regularity  of  the  revolutions,  and  in  the  hands  of  incom- 
petent keepers  are  operations  of  difficulty. 

To  obviate  these  inconveniences,  this  is  the  way  I  have  proceeded. 
Preserving  the  same  number  of  rollers,  I  caused  them  to  be  placed 
between  two  conical  surfaces  having  a  common  centre;  in  that  way  I 
have  obtained  the  regular  development  of  movement  following  the 
generation  of  the  surface  of  revolution. 

Lens  apparatus  for  lighting  sea  steamers  from  their  wheel-louses  and 
boivs,  by  T  .  Letourneau. 

I  find  myself  conducted  in  descending  the  ladder  of  applications  of 
optics,  to  acquaint  you  with  the  last  modification,  that  of  lights  to 
prevent  collision  at  sea. 

The  result  of  detailed  experimental  researches  made  by  some  of 
my  friends  among  the  officers  of  the  French  navy,  has  been  to  engage 
me  to  construct,  according  to  the  ordinance  regulating  it,  small  ap- 
paratus for  colored  lights  to  produce  a  light  sufficiently  intense  to  be 
distinguished  (if  a  white  light)  ten  miles  in  good  weather.  In  conse- 
quence of  the  success  with  which  I  have  met  in  these  lamps,  I  find 
myself  within  the  last  two  years  charged  with  the  supplying  of  all 
that  are  required  for  the  navy  and  for  the  commercial  marine,  both 
of  which  are  subjected  in  the  ordinance  to  the  same  general  rules. 

I  do  not  know  if  the  United  States  has  taken  steps  in  this  impor- 
tant matter  similar  to  those  of  the  British  Parliament  and  of  the 
ordinance  of  Gen.  Cavaignac,  to  insure  a  uniformity  in  the  manner 
of  distinguishing  steamers  at  night  at  sea,  and  to  determine  at  con- 
siderable distances  the  courses  steered. 

SERVICE  AND  REPAIR  OF  THE  APPARATUS. 

No  changes  worthy  of  note,  so  far  as  I  know,  have  been  introduced 
into  the  regulations  relating  to  the  lighting  service,  except  such  as 
relate  specially  to  the  modification  of  the  apparatus,  and  which  may 
have  been  considered  worthy  of  the  attention  of  those  to  whom  they 
were  entrusted  with  a  view  to  test  their  applicability. 

Lamps. 

There  are  at  present  two  descriptions  or  systems  of  lamps,  that  of 
Mr.  Henry  Lepaute  and  mine;  there  is  also  a  third  one  undergoing 


76 

trial,  but  which,  however  highly  recommended  for  its  simplicity,  is 
yet  suffering  from  doubts  as  to  its  durability  and  the  regularity  with 
which  it  will  perform.  I  have  had  for  two  months  one  of  these 
new  lamps  placed  on  board  of  a  steamer  running  at  night  on  the 
river  Rhone;  but.  besides  not  having  received  reliable  intelligence 
in  relation  to  it,  that  experiment  would  not  prove  any  thing,  even  if 
it  were  satisfactory.  The  present  question  is  between  the  two  first 
lamps. 

As  you  are  already  aware,  sir,  that  while  M.  Henry  Lepaute's 
lamp  succeeded  the  Carcel  lamp,  mine  has  succeeded  his.  The  sys- 
tem of  M.  Henry  Lepaute  was  announced,  at  its  introduction,  as  pos- 
sessing superior  qualities  of  combination,  while  mine  has  travelled 
on  its  own  way  noiselessly. 

My  lamp  is  the  counterpart  of  Mr.  Lepaute's:  it  is  the  solidity  of 
it  which  gives  it  the  most  merit,  in  my  opinion. 

To  bring  at  once  this  delicate  subject  to  a  close,  I  would  desire 
that  the  commission  make  a  trial  of  both  lamps. 

Lamp  icicks. 

For  some  time  past  I  have  been  making  trial  of  different  tissues 
for  wicks.  The  object  of  these  researches  was  to  get  rid  of  the  ope- 
ration of  trimming  the  wicks  during  the  night.  I  have  long  known 
how  prejudicial  the  operation  is  to  the  service,  but  I  have  been  com- 
pelled to  abandon  the  subject. 

Lens  apparatus  constructed  ly  me  for  Frame,  England,  Scotland,  Ire- 
land, Spain,  cC-c.,  since  1835. 

In  furnishing  the  list  of  apparatus  constructed  for  these  different 
countries,  I  cannot  say  that  it  contains  all;  by  other  hands  you  will 
receive  the  complement.  Mr.  Wilkins,  of  London,  informs  me  that 
he  will  forward  to  you  a  list  of  the  lights  put  up  in  England,  Ireland 
and  Portugal,  the  great  part  of  the  optical  parts  of  which  I  have 
supplied.  You  will  find  from  page  3  to  7  of  my  notice,  the  table  of 
apparatus  constructed  by  me  before  and  since  1845.  excepting  those 
of  England,  Ireland  and  Portugal,  which  I  have  sent  often  without 
knowing  their  destination. 

Value  of  tJie  apparatus. 
The  price  of  the  apparatus  has  not  changed. 


77 


Oil  for  illuminating  light-houses. 

All  the  experiments  which  have  been  making  for  u  long  time  upon 
the  different  kinds  of  oils,  have  given  results  showing  them  to  be  in 
every  respect  inferior  to  that  obtained  from  colza.  The  rich  oleagin- 
ous quality  of  that  grain,  and  the  quantity  of  land  prepared  for  its 
culture,  have  rendered  it  of  great  importance  ;  besides  which,  the 
oil  is  now  prepared  in  the  most  perfect  manner.  A  friend  of  mine  in 
Normandy,  who  is  familiar  with  the  modes  of  preparing  the  land  for 
the  culture  of  this  plant,  has  promised  to  address  me  shortly  on  the 
subject,  and  furnish  to  me  in  detail  an  exact  account  of  the  process. 
For  the  present,  I  must  confine  myself  to  the  following  hints  : 

Rich  land  is  preferred  for  the  cultivation  of  the  colza :  but,  how- 
ever, it  is  commonly  the  custom  in  Normandy  to  sow  the  colza  upon 
the  fields  from  which  wheat  has  been  cut.  The  north  of  France  is 
its  peculiar  region. 

Markets. 

The  principal  markets  for  colza  oil  are  :  for  the  north  of  France, 
Lille  and  Coutrai,  and  for  the  west,  Caen  and  Rouen.  The  price  is 
necessarily  variable,  its  average  rate  is  72  francs  the  hectoliter  for 
the  first  quality  clarified.*  The  prices  may  differ  greatly  at  certain 
ports  for  transhipment,  depending  upon  the  small  or  large  number  of 
emigrants  applying  for  passage. 


MARINE  SURVEYOR'S  OFFICE, 
V        Liverpool,  November  20,  1851. 

SIR  :  I  regret  that  my  absence  from  Liverpool  for  a  long  period,  in 
consequence  of  ill  health,  should  have  caused  your  letter  from  the 
Light-house  Board  of  the  United  States  to  remain  so  long  unanswered. 
Having  only  recently  returned  to  my  official  duties,  I  now  hasten 
to  reply  to  the  question  proposed  in  your  communication  of  May  last, 
which,  I  trust,  will  be  found  satisfactory,  and  should  further  informa- 
tion, or  explanation  of  any  matter  connected  with  the  marine  depart- 

«A  hectoliter  is  a  little  over  26  gallons,  making  the  price  of  the  first  quality  clarified 
colza  oil  in  France  55£  cents  per  gallon,  while  sperm  oil  ranges  in  this  country  from  $1 
to  $1  50  per  gallon. 


78 

ment  at  this  port,  be  required  by  the  Light-house  Board  of  the  United 
States,  both  the  dock  committee  and  myself  will  have  much  pleasure 
in  furnishing  it. 

1.  No  change  has  been  made  in  the  mode  and  materials  for  light- 
houses at  this  port. 

2.  The  best  description  of  mortar  for  resisting  the  action  of  salt 
water,  &c.,  is  that  composed  of  sand,  lime,  smithy  ash  ;  and  the  best 
coating  for  light  towers,  is  paint  made  of  pure  white  lead,  with  sand 
thrown  on  it  while  the  paint  is  in  a  liquid  state. 

3.  No   Fresnel  lights  have   been  introduced  here.      Parabolic  re- 
flectors of  twenty-one  inch  diameter  are  in  general  use  at  the   light- 
houses, with  the  exception  of  the  two  Hoylake  light-houses,  in  which 
parabolas  of  twenty-nine  and  twenty-seven  inches  are  used. 

Refined  olive  oil  has  been  introduced  and  burnt  at  the  various 
light-houses  and  light  ships,  instead  of  sperrn  oil.  Since  the  year 
1847,  the  saving  in  cost  price,  as  compared  with  sperm  oil,  is  about 
forty  per  cent. :  and  the  illuminating  powers  are  fully  equal,  if  not 
superior,  to  those  of  sperm  oil. 

4.  The  best  reflector  in   use  is  the   parabolic.      The  proportion  of 
silver  used  here  is   six  ounces   to   the   pound  avoirdupois  of  copper. 
They   are  made  of  various  prices  and    qualities,    varying  from  two 
ounces  to  six  ounces  of  silver  to  the  pound  of  copper.     Their  illumi- 
nating  powers  and  focal  distance  of  lamp  burner  from  reflector,  are 
tested  with  those  in  use  by  means  of  the  intensity  of  the  light  re- 
flected by  them. 

5.  Argand  lamps  are  used  in  reflector  shore  lights. 

(j.  The  ventilation  in  the  shore  lights  is  effected  by  a  chimney  and 
turn-cap  on  the  summit  of  the  light-room  or  lantern  ;  air  valves  in 
window  frames  and  sides  of  light-room  ;  and  copper  tubes  over  the 
lamp  cylinders  to  carry  oif  the  smoke. 

7.  The  materials  of  lanterns  in  the  light-houses  and  sizes  of  glass 
vary  considerably.  In  the  Crosby  light-house,  (one  of  the  last  erect- 
ed,) the  lantern  is  of  wood,  lined  with  sheet  iron  ;  the  window  frames 
of  iron  ;  the  panes  of  glass,  of  which  there  are  three,  are  of  the  di- 
mensions of  six  feet  by  three,  glazed  with  putty  and  pins.  The  as- 
tragals are  vertical,  and  although  very  strong,  obstruct  very  little 
light.  In  the  Rock  light-house,  built  after  the  plan  of  the  Eddy- 
stone  light-house,  the  window  frames  and  roof  of  lantern  are  of 
copper  ;  there  are  sixteen  squares  of  glass  in  the  round,  four  ditto 


79 

in  depth  ;  the  squares  are  two  feet  five  inches  by  two  feet ;  the  lan- 
tern is  fifteen  feet  six  inches  in  diameter  :  the  astragals  are  vertical 
and  horizontal. 

8.  The  burners  of  the  lamps  are  tipped  with  silver  to  prevent  their 
too  rapid  decay  from  the  action  of  the  flame. 

9.  The  best  parabolic  reflectors,  after  being  twenty  years  in  use 
with  good  care  and  attention,  are  not  perceptibly  deteriorated.    The 
inferior  quality  are  not  used  here. 

10.  A  set  of  the  best  lamps,  with  silver-tipped  burners,  with  good 
cure  and  attention,  will  last  twenty  or  thirty  years,  with  occasional 
repairs  and  the  renewal  of  the  burners,  which  last  on  an  average  three 
or  four  years. 

11.  The  repairs  of  illuminating-  apparatus  are  made  under  the  di- 
rection and  superintendence  of  the  dock  and  marine  surveyors. 

12.  The  lamps  and  reflectors  in  the  light-ships  are  not  mounted  on 
gimballs ;  but  parabolic  reflectors  of  21  inches  diameter,  similar  to 
those  in  the  light-houses,  are  used  in  the  light  ships,  and  lamps  with 
a  flat  wick  two  inches  wide  ;  the  oil  cistern  is  placed  at  the  back  of 
the  reflector,  and  the  cistern  is  ingeniously  subdivided  by  partitions 
perforated  with  holes,  to  prevent  the  flooding  of  the  oil  by  the  ship's 
motion.     The  introduction  of  these  improved  light-ships,  lanterns, 
and  reflectors,  by  which  a  light  is  produced  equal  to  that  shown  from 
the  light-houses,  is  due  to  Mr.  Hartley,  dock  surveyor  to  the  Liver- 
pool dock  trustees. 

13.  The  greatest  improvement  made  in  the  light-ship's  moorings, 
is  the  introduction  of  wrought-iron  welded  studs  in  the  chains,  in- 
stead of  the  common  cast-iron  studs.     These  improved  chains  arc 
used  in  the  thirty  fathom  lengths  next  the  bows  of  the  light-vessels, 
and  the  chains  have  been  found  to  break  much  less  frequently  than 
they  did  prior  to  their  introduction.     The  remaining  portion  of  the 
light-ship's  moorings  are  of  the  ordinary  stud-chain. 

The  buoy  moorings  vary  in  size,  according  to  the  dimensions  of  the 
buoys  ;  the  chains  are  made  without  any  studs  ;  the  sinkers  are  of  the 
shape  and  size  shown  in  the  accompanying  drawing. 

14.  The  fog  signals  in  use  at  the  light-houses  and  light-ships  con- 
sist of  bells  and  gongs. 

15.  The  material  I  should  recommend  for  buoys,  floating  beacons, 
and  light-vessels,  is  iron.     The  colors,  shapes,  distinguishing  marks, 
<fcc.,  are  shown  on  the  chart  of  Liverpool  bay,  of  which  I  send  you  a 
copy. 


80 

10.  The  buoys  and  light-ships  are  placed  and  moored  in  their 
positions  by  cross-marks  and  sextant  angles  ;  and  a  register  is  kept 
in  the  marine  surveyor's  office  of  every  circumstance  connected  with 
them,  according  to  form  No.  1,  sent  herewith. 

The  light-ships'  moorings  are  hove  up  and  examined  as  far  down  as 
possible,  on  every  favorable  occasion  :  they  are  entirely  hove  up,  and 
the  worn  parts  renewed  annually.  Duplicate  light-vessels  and  buoys 
<tre  kept  ready  for  instant  use.  A  buoy-tender  manned  by  the  shore 
party  of  the  light-ships'  crews,  executes  the  buoy  service,  heaving  up 
the  moorings,  <fcc. 

The  number  of  officers  and  men  employed  on  board  the  light-ships, 
will  be  found  in  the  light-ships'  rules  sent  herewith. 

The  masters  of  the  light-ships  arc  relieved  every  month  ;  the  sea- 
men serve  two  months  on  board,  and  one  month  on  shore. 

For  relieving  shipwrecks,  etc.,  the  dock  committee  have  established 
iive  life-boat  stations  in  Liverpool  bay,  the  rules  and  regulations  for 
which  I  send  herewith  ;  also  a  copy  of  my  report  to  the  shipwreck 
committee,  which  contains  all  the  information  vou  require  under  this 
head. 

The  annual  expense  of  this  branch  amounts  on  an  average  to  =£1, 900. 

Every  branch  of  the  marine  department  is  inspected  monthly,  either 
by  the  marine  surveyor  or  his  assistant. 

IT.  The  appointment  of  light-keepers,  A:e.,  are  made  by  the  dock 
committee. 

The  instructions  to  the  light -keepers  are  enclosed  herewith,  num- 
bered from  7  to  13. 

18.  Iron-rod  electrical  conductors  are  employed. 

19.  The  oils  are  tested  by  their  specific  gravity,  burning,  and  the 
intensity  of  the  light  produced. 

The  chain  moorings,  both  for  buoys  and  light-ships,  are  tested  at 
the  corporation  testing  machine. 

20.  The  system  on  which  lights  are  masked  at  this  port,  is  shown 
on  the  accompanying  chart  of  Liverpool  bay  ;  the  object  being  to 
point  out  to  the  mariner,  by  the  opening  and  shutting  of  the  lights, 
when  he  is  to  alter  his  course  in  the  channel,  or  at  the  elbows  of 
banks,  <fcc.     It  also  indicates  the  position  of  the  Northwest  and  Cros- 
by light-vessels,  in  the  event  of  those  vessels  parting  their  moorings, 
and  being  absent  from  their  stations.     It  may  be  effected  by  means 
of  blinkers  placed  on  the  windows  of  old  light-houses,  and,  in  new 
ones,  by  the  construction  of  the  window  frames. 


81 

21.  The  modes  of  distinguishing  lights  are  fixed,  revolving,  and 
flashing  ;  the  colors  are  red  and  u'hite. 

The  light- vessels  show  one,  two,  or  three  lights  by  night ;  and  a 
large  ball  at  the  mainmast  head  by  day  ;  they  are  also  distinguished 
by  the  color  of  their  paint. 

The  light-towers  are  painted  white,  red  and  white,  or  Hack  and  white, 
according  to  locality  and  background  ;  the  sea-marks  are  painted 
either  Hack,  or  white,  or  striped,  according  to  locality  and  background. 

In  renewing  our  correspondence,  permit  me  to  express  to  you  the 
high  sense  I  entertain  of  the  favorable  opinion  and  disinterested  ap- 
probation which  you  were  pleased  to  bestow  on  the  marine  establish- 
ment at  this  port ;  and  allow  me  at  the  same  time  to  congratulate  you 
on  the  adoption,  by  the  United  States  government,  of  the  valuable 
recommendations  and  suggestions  contained  in  the  very  able  report 
of  yourself  and  Lieutenant  Bache,  in  184G  ;  and  wishing  you  every 
success  in  the  highly  important  and  arduous  duties  that  lie  before 
you,  I  beg  to  subscribe  myself, 

With  sincere  esteem  and  respect,  your  obedient  servant, 

WM.  LORD. 

Lieut.  THORNTON  A.  JENKINS, 

Sec'y  U.  S.  Light-house  Board,   Washington. 


MARINE  SURVEYOR'S  OFFICE, 

Liverpool,  October  16,  1843. 

SIR  :  In  compliance  with  the  instructions  of  the  sub-committee  on 
shipwrecks,  that  I  should  report  on  the  life-boat  establishment  of 
this  port,  and  the  extent  and  nature  of  the  banks  in  Liverpool  bay,  I 
have  to  submit  the  accompanying  statement : 

There  are  nine  life-boats  stationed  as  follows,  viz  : 

Liverpool 2  boats,  1  master,  and  10  men. 

-» I-          •  9      » '        i        * '  10" 

Magazines * 

Hoylake 2     "      -1       » 

PointofAir 2  10     ' 

Formby 1 

Nearly  all  the  boats  have  been  built  since  1839.    They  pull  double- 
banked,  are  rigged  with  two  sprit-sails  and  a  jib,  are  of  large  size, 
possess  great  strength,  and  are  constructed  on  the  most  approved 
6 


82 

principles,  with  air-tight  casks  inside,  and  a  broad  band  of  cork  run- 
ning round  the  whole  length  of  the  boat,  above  the  water-line,  to  re- 
sist violent  shocks  and  give  increased  buoyancy,  enabling  the  boat  to 
float,  although  loaded  with  a  considerable  number  of  persons  and  filled 
with  water  ;  as  many  as  fifty  individuals  having  on  one  occasion  been 
rescued  from  a  wreck  at  one  trip,  making,  with  the  boat's  crew  of 
eleven,  sixty-one  persons  in  the  boat  at  one  time. 

The  boats  are  kept  on  carriages  in  the  boat-houses  near  the  shore, 
and  horses  are  provided  to  enable  them  to  proceed  to  the  most  ad- 
vantageous spot  for  launching.  A  gun  is  placed  at  the  station  to 
summon  the  crew,  as  also  distance-flags  at  each  light-house,  light- 
ship and  telegraph  station,  for  the  same  purpose  ;  the  arrangements 
in  these  respects  being  such,  that  in  many  instances  the  life-boat  has 
been  manned,  launched,  and  on  her  way  to  the  wreck  in  seventeen 
or  eighteen  minutes  from  the  time  of  the  distress-signal  being  seen. 

The  masters  and  crews  of  the  Hoylake,  Magazines  and  Formby 
boats  are  composed  of  picked  fishermen,  intimately  acquainted  with 
the  banks,  swash  ways,  tides  and  currents  in  Liverpool  bay.  They 
reside  in  the  immediate  vicinity  of  their  respective  boat-houses. 

The  Liverpool  boat's  crew  consists  of  experienced  boatmen  resid- 
ing in  the  town. 

The  Point  of  Air  boat's  crew  consists  of  two  experienced  Hoylake 
fishermen  as  master  and  mate  of  the  boat.  These  men  have  been 
engaged  for  the  last  four  years,  at  an  increased  annual  salary,  expressly 
for  the  purpose  of  organizing  this  boat's  crew,  and  the  rest  of  the 
crew  are  selected  from  the  best  and  most  expert  men  that  can  be  found 
in  the  neighborhood. 

The  whole  of  the  crews  are  kept  in  constant  and  permanent  pay. 
They  are  regularly  mustered  and  exercised  once  a  month,  and  no 
expense  has  been  spared  in  rendering  the  boats,  their  equipments, 
and  crews,  as  perfect  as  possible. 

The  Hoylake  boat  is  under  the  active  and  vigilant  superintendence 
of  Mr.  Sherwood,  revenue  surveyor  at  Hoylake;  the  Point  of  Air 
boat  under  that  of  Mr.  Dawson,  of  Grovant,  and  the  Formby  boat 
under  the  direction  of  the  keeper  of  the  Crosby  light-house. 

The  banks  and  dangers  in  Liverpool  bay  may  all  be  comprised 
within  a  triangle  formed  by  the  western  patch  of  West  Hoyle,  the 
Rock  light-house,  and  Mad  wharf— the  former  (West  Hoyle)  distant 
from  Liverpool  nineteen  nautical  miles,  the  latter  (Mad  wharf)  twelve 
nautical  miles;  the  cross  distance  between  West  Hoyle  and  Mad 
wharf  being  sixteen  miles. 


83 

The  principal  banks  are  West  Hoyle,  East  Hoyle,  Great  and  Little 
Burbo,  the  Jordan  flats,  Burbo  flats,  Mad  wharf,  Mockbeggar  wharf, 
Formby  bank,  and  Taylor's  bank.  They  are  all  remote  from  Liver- 
pool, and  many  of  them  several  miles  distant  from  the  nearest  life- 
boat station — many  patches  of  all  the  banks  dry,  and  some  of  them 
to  a  considerable  height  above  the  low- water  level;  but  in  heavy, 
on-shore  gales  of  wind,  owing  to  the  shallowness  of  the  water,  a 
continuous  line  of  heavy  breakers  extends  far  to  seaward  on  the 
weather  side  of  them,  rendering  it  extremely  difficult,  and  at  times 
perfectly  impracticable,  however  advantageously  the  boats  may  be 
placed,  and  however  near  they  may  attain  the  position,  to  penetrate 
to  a  wreck  so  situated,  without  the  certain  and  inevitable  destruction 
of  the  life-boat  and  her  crew.  This  has  been  strongly  exemplified 
in  the  cases  of  the  Athabasen  arid  the  Despatch,  lost  on  "West  Hoyle. 
In  both  instances,  the  life-boats  reached  the  scene  of  the  disaster, 
although  four  miles  distant  from  Point  of  Air,  and  ten  from  Hoylake 
stations,  but  were  obliged  to  abandon  the  crews  to  their  fate,  after 
repeated  attempts  to  penetrate  the  line  of  breakers  extending  out- 
side of  them.  Numerous  instances  of  a  similar  nature  might  be 
adduced,  occurring  to  vessels  lost  on  the  sand  banks  on  the  east  coast 
of  England;  one,  in  particular,  recurs  forcibly  to  my  memory — that 
of  the  "Ogle  Castle"  Indiaman,  lost  on  the  Goodwin  sands.  In  this 
case,  the  Deal  boats  were  so  near  as  distinctly  to  see  the  successive 
surges  sweep  away  the  unfortunate  crew  from  the  deck  and  rigging, 
without  being  able  to  render  the  slightest  assistance. 

The  remoteness  of  the  banks  from  the  land,  and  the  long  line  of 
shoal  water  extending  from  them,  renders  the  use  of  all  projectiles, 
such  as  mortars,  rockets,  Ac.,  inapplicable  in  Liverpool  bay,  as  it 
very  seldom  happens  that  a  wreck  can  be  approached  sufficiently 
near  to  render  them  available. 

In  face,  however,  of  all  the  natural  difficulties  which  Liverpool 
bay  presents  under  these  circumstances,  and  with  the  immense 
amount  of  shipping  which  enters  and  quits  the  port,  it  must  be  a 
gratifying  fact  for  the  committee  to  know,  that  for  the  last  four  and 
a  half  years  only  one  call  (that  of  the  "Despatch"  sloop,  lost  on 
West  Hoyle)  has  occurred,  in  which  the  life-boats  could  not  render 
assistance,  owing  to  the  circumstances  above  shown;  whilst  in  the 
same  period  no  less  than  seventy-four  vessels  have  been  assisted,  and 
four  hundred  and  fifteen  lives  preserved  by  their  life-boat  estab- 
lishment, owing,  no  doubt,  chiefly  to  the  judicious  position  of  the 


84 

life-boat  stations,  by  which  one  or  other  of  the  boats  has  always 
been  able  to  reach  the  scene  of  the  wreck;  and  lastly,  to  the  perfect 
confidence  the  crews  feel  in  their  boats,  and  the  praiseworthy  exer- 
tions they  have  invariably  shown  in  the  performance  of  their  duties. 

To  facilitate  the  operations  of  the  life-boats,  an  arrangement  is  in 
existence  with  the  steam-tug  company,  by  which  one  of  their  steamers 
is  to  proceed  out  immediately  the  signal  of  distress  is  seen  flying, 
taking  in  tow  the  first  life-boat  that  reaches  her,  whether  their  own 
or  one  belonging  to  the  Dock  Trust,  or  both,  if  the  weather  will  per- 
mit of  it. 

In  order  to  point  out  and  identify  the  exact  spot  to  which  the 
steamer  or  life-boats  are  to  proceed,  the  Avhole  of  Liverpool  bay  and 
the  coast,  thence  to  Holyhead,  has  been  divided  into  squares,  num- 
bered consecutively  on  the  chart,  each  light-house,  light-ship,  and 
telegraph  station,  etc..  being  provided  with  such  chart,  and  the 
keeper  directed  to  report,  by  signal,  the  number  of  the  square  in 
which  any  wreck  may  occur. 

I  am,  sir,  your  obedient  servant, 

WM.  LORD. 

To  the  Chairman  of  the  Sal- Committee  on  Shipwrecks. 


Letter  from  Thomas  Stevenson,  F.R.S.E.,  F.It.S.S.A. 

EDINBURGH,  August  7,  1851. 

SIR:  In  the  absence  of  my  brother,  I  beg  to  acknowledge  the 
receipt  of  your  letter  of  the  27th  May. 

Having  carefully  perused  the  list  of  queries  embraced  in  your  com- 
munication, I  beg  leave  to  direct  your  attention  to  my  brother's 
account  of  the  Skerryvore  light-house,  and  notes  on  light-house  illu- 
mination, published  in  1848,  and  to  his  more  recent  publication  enti- 
tled "  A  Rudimentary  Treatise  on  Light-houses,"  &c.,  published  by 
Mr.  Weale,  of  London,  in  1850.  I  think  you  will  find  answers,  so 
far  as  they  are  known,  to  your  queries  in  both  of  these  books,  but 
especially  in  the  "Rudimentary  Treatise."  I  may  state  the  follow- 
ing, however,  as  they  may  not  be  so  explicitly  given  in  either  treatise. 

1.  I  am  not  aware  that  any  of  the  slide  lamps  have  ever  been  worn 
out 


2.  Nothing  Las  occurred  to  shake   confidence  in  the  concentric 
burner  of  Fresnel. 

3.  The  same  kind  of  oil  is  used  in  the  northern  light-houses,  both 
in  summer  and  winter. 

4.  The  electric  conductors,  which  are  of  copper,  are  three -fourths 
of  an  inch  in  diameter,  and  tipped  with  platinum  or  palladium. 

5.  There  is  no  difference  in  the  number  of  light  keepers  for  lens 
lights  and  catoptric  lights. 

G.  No  light  keeper  is  allowed  to  leave  the  light-room  a  moment 
before  the  arrival  of  his  successor. 

7.  None  of  the  northern  light- houses  have  their  characteristic  dis- 
tinctions altered. 

I  send  you,  with  this,  three  copies  of  a  pamphlet  just  published, 
which  contains  the  most  recent  improvements  of  which  I  am  aware. 
These  improvements  constitute  what  I  have  called  the  Holophotal 
system  of  illumination,  which,  by  transmitting  all  the  divergent  rays 
of  a  flame  without  unnecessary  reflection  or  refraction  in  one  parallel 
beam,  thus  gives  out  the  maximum  effect  of  the  lamp.  You  will  find 
a  reference  to  this  system  at  p.  142,  part  I,  of  my  brother's  treatise. 

Although  only  very  recently  proposed,  we  have  successfully  intro- 
duced it  at  five  different  places,  and  another  light  is  just  about  being 
got  ready. 

I  remain,  sir,  your  most  obedient  servant, 

THOMAS  STEVENSON. 

Lieut.  THOKNTON  A.  JENKINS,  U.  S.  N., 

Secretary  to  Ligld-liouse  Board,   Washington,  D.C. 


Northern  Lights. 

LENS  COMMITTEE,  February  23,  1833. 

Present :  J.  A.  Maconochie,  esq.,  James  L.  Amy,  esq.,  Andrew 
Murray,  esq.,  Archibald  Bell,  esq. 

The  convener  laid  before  the  meeting  the  following  communication 
from  Sir  David  Brewster,  in  regard  to  the  comparative  merits  of  lens 
and  reflector  lights. 

"I  take  the  liberty  of  addressing  you  as  convener  of  the  Light- 
house Committee,  on  the  comparative  value  and  economy  of  lenses 
and  reflectors,  and  of  suggesting  some  additional  experiments  for 


86 

exhibiting  the  superiority  of  the  former.  I  need  not  mention  to  you, 
that  the  most  distinguished  philosophers  in  the  institute,  and  the 
most  celebrated  engineers  and  naval  officers  in  France,  have,  on  the 
authority  of  direct  experiments,  decided  in  favor  of  lenses,  both  as 
to  effect  and  economy. 

"The  Academy  of  Science  at  St.  Petersburgh  have  done  the  same 
more  than  five  years  ago,  and  Sir  John  Herschel  has  lately  published 
the  following  testimony  in  their  favor.  'The  light-house,'  says  he, 
'  with  the  capital  improvements  which  the  lenses  of  Brewster  and 
Fresnel,  and  the  elegant  lamp  of  Lieut.  Drummond,  have  conferred 
and  promise  yet  to  confer,  by  their  wonderful  powers,  the  one  of 
producing  the  most  intense  light  yet  known,  the  others  of  conveying 
it  undispersed  to  great  distances.'  Disc,  on  Nat.  Phil.,  p.  56. 

k :  The  superiority  of  lenses,  however,  is  no  longer  a  matter  of  opin- 
ion, for  it  was  proved,  in  the  presence  of  the  committee,  that  a  single 
lens  was  equal  to  at  least  nine  reflectors. 

"This  lens,  too.  was  only  twenty-nine  inches  in  diameter,  and  was 
of  green  crown  glass.  Had  it  been  made  of  good  flint  glass,  and 
been  thirty-six  inches  in  diameter,  it  wonld  have  been  equal  to  at 
least  fourteen  reflectors,  four  being  added  for  the  increase  of  area, 
which  is  a  matter  of  simple  calculation,  and  one  for  the  loss  of  light 
in  the  green  glass.  I  shall  not  avail  myself,  however,  of  this  undoubted 
fact,  but  shall  take  the  result  which  was  actually  seen  by  the  com- 
mittee, namely,  that  one  lens  equals  nine  reflectors,  and  I  shall  apply 
it  to  the  case  of  a  revolving  light. 

"The  revolving  light  with  lenses  will  consist  of  two  lenses  placed 
opposite  to  each  other,  and  illuminated  by  a  single  lamp  between 
them.  The  revolving  light  with  reflectors  will  consist  of  eighteen 
Argand  burners,  nine  reflectors  being  substitutes  for  each  lens. 

"It  being  admitted  that  these  two  pieces  of  apparatus  will  give 
the  same  light,  let  us  consider  their  comparative  advantages: 

"  1st.  The  lens  apparatus  will  be  decidedly  the  cheapest  in  its  first 
cost,  and  the  lenses  will  never  require  to  be  renewed. 

"2d.  The  lens  apparatus  will  not  require  one-third  of  the  labor 
in  cleaning  and  arranging  them  daily  for  use. 

"3d.  The  lens  apparatus  will  not  require  so  strong  and  powerful 
a  piece  of  machinery  to  move  it,  from  its  inferior  weight  and  its 
greater  compactness. 

"4th.  The  lens  apparatus  may  be  placed  in  a  much  smaller  light- 
room,  the  eighteen  reflectors  requiring  a  very  large  space,  and  econ- 
omy might  thus  be  introduced  in  the  erection  of  future  light-houses. 


87 

"5th.  The  eighteen  Argand  burners  will  decidedly  consume 
more  oil  than  the  simple  compound  burner  used  for  the  lenses;  hence  it 
follows  that  the  lens  apparatus  is  in  every  respect  better  and  more 
economical  than  the  reflector  apparatus. 

' '  But  in  the  above  comparison  I  have  omitted  entirely  the  addition 
of  the  lateral  lenses  and  mirrors  which  I  proposed  in  1811,  and  which 
were  used  in  the  French  light-houses.  These  lenses  and  mirrors  will 
enable  us  to  take  as  much  light  from  the  compound  burner  (which 
otherwise  goes  to  waste)  as  will  be  equal  to  four  reflectors  at  the  very 
least;  so  that  without  the  slightest  additional  expense,  excepting  the 
original  cost  of  these  small  lenses,  &c.,  we  can  give  the  lens  appara- 
tus a  great  superiority  over  the  reflector  apparatus. 

' '  Let  us  now  compare  the  lenses  and  reflectors  in  reference  to  the 
introduction  of  extraordinary  illumination,  which  in  fogs  and  in  sea- 
sons of  danger  may  be  required. 

"The  means  which  may  be  thus  resorted  to  are  these:  1st,  the 
Drummond  light;  2d,  the  blue  and  signal  lights;  and  3d,  any  extra 
lamps  which  may  be  at  the  time  in  the  light-house. 

"In  the  lens  apparatus  the  Drummond  light  can  be  introduced 
instantly,  by  merely  putting  the  lime-ball  in  the  place  of  the  burner. 
In  the  reflector  apparatus  this  is  impossible.  To  produce  the  same 
effect  the  eighteen  reflectors  would  require  to  be  each  fitted  up  with 
a  Drummond  light,  the  expense  of  which  would  be  enormous,  and 
for  ordinary  and  extraordinary  purposes  the  light-house  would  require 
in  all  thirty-six  reflectors,  to  be  as  effective  as  the  lens  apparatus. 

"In  introducing  the  blue  and  red  lights  for  occasional  purposes, 
we  have  or.ly  to  burn  them  on  an  iron  plate  or  dish,  placed  either 
beside  the  burner  or  occupying  its  position.  From  the  power  of  the 
red  light  to  penetrate  fogs,  I  consider  it  as  an  invaluable  resource  in 
light-houses.  In  the  experiment  which  the  commissioners  witnessed, 
its  brilliancy  was  fully  equal  to  that  of  the  lens  apparatus.  I  need 
scarcely  add  that  these  signal  lights  cannot  be  introduced  into  reflec- 
tors. 

"If  the  light-house  keeper  is  provided  neither  with  the  Drummond' 
light  nor  the  blue  and  red  signal  fires,  he  can  at  present  do  nothing 
to  add  a  ray  to  his  reflectors,  even  if  he  knew  that  in  a  dark  and 
stormy  night  human  life  is  exposed  to  danger.  With  the  lens  appa- 
ratus, on  the  contrary,  he  can  surround  the  main  burner  with  all  the 
spare  Argand  burners  in  his  possession,  and  thus  convey  a  great 
quantity  of  additional  light  into  the  refracted  beam. 


88 

"Hence  it  follows  that  the  lens  apparatus  is  far  more  intense  than 
a  reflector  apparatus  of  the  same  size  ;  that  with  the  same  intensity 
of  light  it  consumes  much  less  oil  ;  that  in  reference  to  original  cost, 
repairs  and  renewals,  it  is  more  economical,-  that  it  requires  a  less  ex- 
pensive light-room,  and  demands  much  less  time  and  trouble  from  the 
keeper,  while  it  possesses  the  property  (which  reflectors  never  can 
have)  of  admitting  every  variety  of  resource  in  cases  which  demand 
extraordinary  illumination. 

"I  have  no  scruple  in  stating  that  the  introduction  of  the  lens  ap- 
paratus will  occasion  an  annual  saving  in  the  expenditure  of  the  board: 
but  if  this  were  not  the  case,  and  if  much  more  oil  were  consumed  by 
the  use  of  superior  lights,  it  would  still  be  the  duty  of  the  commis- 
sioners to  adopt  it.  No  mining  company  uses  the  old  steam  engines 
of  Savary  and  Newcomens  in  order  to  save  the  additional  expense  of 
purchasing  one  of  James  Watt's.  Xo  astronomer  continues  to  use 
the  old  refracting  telescope  because  an  achromatic  telescope  is  a 
dearer  instrument.  In  these  case.?  scientific  and  pecuniary  interests 
are  alone  concerned  :  but  in  the  choice  of  lights,  human  life  is  in- 
volved, as  well  as  national  property,  and  a  higher  responsibility  is 
therefore  attached  to  their  management.  I  trust,  therefore,  that  the 
commissioners,  now  that  they  have  witnessed  the  superiority  of  lenses, 
will  not  allow  any  considerations  of  economy  (even  if  they  did  exist) 
to  prevent  them  from  introducing  a  system  of  illumination  already  es- 
tablished in  other  countries,  and  calculated  to  promote  the  just  ob- 
jects for  which  their  board  was  instituted. 

"  In  order  to  prove  more  fully  the  value  of  lens  illumination,  I  beg- 
to  suggest  the  following  experiments  and  calculations  : 

"1.  Try  the  Drummond  light  in  the  focus  of  the  lens,  and  compare 
it  with  the  same  light  in  the  focus  of  a  reflector. 

1;2.  Try  the  blue  and  red  lights  in  the  focus  of  the  lens. 

•'3.  Compare  a  single  reflector  with  the  same  Argand  burner  in 
the  focus  of  the  lens. 

'•4.  Compare  the  quantity  of  oil  consumed  by  one  compound 
burner  with  that  consumed  by  eighteen  Argand  burners  of  the  common 
size. 

"5.  Compare  the  expense  of  a  light-house  erected  for  a  revolving 
lens  apparatus,  with  that  of  one  erected  for  eighteen  reflectors. 

"6.  Compare  the  expense  of  two  lenses  (£25  each  in  Paris)  with 
that  of  eighteen  reflectors,  adding  the  expense  of  their  frames  and  of 
the  machinery  for  moving  them. 


m 

"Before  concluding  these  hurried  observations,  permit  me  to  add, 
that  the  use  of  distinguishing  lights  is  considered  by  every  person  as 
highly  desirable,  and  that  it  is  only  with  the  lens  apparatus  that  they 
can  successfully  be  introduced.  I  would  beg  leave,  also,  to  repeat 
what  I  urged  on  a  former  occasion,  that  coal  gas  should  be  employed 
in  every  light-house  where  there  is  accommodation  for  its  proper  manu- 
facture. An  immense  saving  wrould  thus  be  effected,  and  a  more  per- 
fect system  of  illumination  obtained. 

"ALLEELY  BY  MELKOSE,    February  16,   1833. 
"J.  A.   MACOXOCHIE,  Esq.,  &c.,  &c." 

And  the  meeting  being  of  opinion  that  the  information  contained 
in  the  above  communication  is  of  the  greatest  importance,  in  the  view 
of  introducing  the  apparatus  into  the  light-houses  in  progress,  direct 
the  report  of  the  engineer  on  the  experiments  already  made,  and  the 
above  communication,  to  be  immediately  reported  to  the  Bell  Rock 
Committee,  to  ascertain  whether  it  could  not  be  done. 

«-  -;:-  -:<-  -::•  -::•  •?•  *  -::- 

The  difference  between  the  original  cost  of  the  reflecting  and  re- 
fracting apparatus  is  of  course  more  or  less  in  proportion  to  the  num- 
ber of  reflectors  or  lenses  employed.  The  expense  at  Paris  of  the 
apparatus  for  the  Tour  de  Cordouan,  where  there  are  nine  vertical 
lenses,  besides  a  system  of  fixed  mirrors,  was  stated  by  M.  Fresnel  to 
be  about  £1,500  ;  but  in  estimating  a  similar  apparatus,  if  again  re- 
quired, he  made  the  amount  28,202  francs,  or  £1,177  11s.  8d.  The 
cost  of  the  reflecting  and  revolving  apparatus,  with  twenty-four  re- 
flectors, is  £1,387.  "With  regard  to  the  annual  expense  and  other 
conditions  of  the  lens  system,  the  engineer  is  not  prepared  to  give  an 
opinion  ;  but  after  a  sufficient  number  of  trials  have  been  made  with 
the  very  complete  apparatus  provided  by  the  board  for  investigating 
this  important  subject,  he  will  be  enabled  to  report  satisfactorily 
upon  the  several  objects  to  which  his  attention  has  been  directed  by 
the  minute  of  the  23d  February.  In  the  meantime,  to  meet  the  ur- 
gent desire  of  the  Lord  Provost  of  Edinburgh,  the  above  estimate  has 
been  prepared  from  his  notes,  made  with  M.  Fresnel  when  at  Paris. 
and  from  his  personal  observations  of  the  Tour  de  Cordouan." 

And  on  motion  of  the  Lord  Provost,  it  was  resolved  to  recommend 
to  a  general  meeting,  to  be  called  for  the  special  purpose,  on  Monday 
next,  at  12  o'clock,  to  have  the  light  at  Inchkeith  immediately  adapt- 
ed to  the  lens  apparatus. 


90 

The  following  communication  was  since  received  by  Mr.  Maeonochie 
from  Sir  David  Brewster  : 

ALLERLY  BY  MELROSE, 

March  29,    1833. 

MY  DEAR  SIR  :  As  the  experiments  made  on  the  Calton  hill  afford 
sufficient  data  for  guiding  the  opinion  of  the  board  on  the  relative 
value  and  economy  of  lenses  and  reflectors,  I  beg  you  will  submit  to 
the  commissioners,  at  their  first  meeting,  the  following  statement 
respecting  some  important  questions  to  which  they  will  no  doubt 
speedily  direct  their  attention  : 

1.  In  establishing  a  new  light-house,  should  the  method  of  illumi- 
nation by  lenses  be  adopted  ? 

2.  Would  it  be  wise  to  dismantle  every  light-house  in  Scotland,  and 
substitute  lenses  for  reflectors  ? 

3.  Should  gas  be  introduced  in  place  of  oil  ? 

4.  Should  means  be  provided  in  every  light-house  for  the  occasional 
exhibition  of  powerful  lights? 

5.  Should  a  new  system  of  distinguishing  lights  be  matured  and 
adopted  ? 

To  all  these  questions  I  trust  the  commissioners  will  agree  with  me 
in  giving  an  affirmative  answer.  That  the  committee  of  the  Royal 
Society  will  concur  in  the  statement  I  am  about  to  make,  I  cannot  for 
a  moment  doubt ;  because  scientific  questions  can  admit  of  only  one 
solution.  But  if,  like  other  prophets,  our  opinions  shall  have  no  weight 
in  our  own  country,  I  shall,  for  the  satisfaction  of  the  board,  be  able 
to  support  them  by  the  concurring  testimonies  of  the  most  distinguish- 
ed professors  in  Cambridge  and  Oxford,  and  by  the  practical  judg- 
ment of  the  most  eminent  scientific  engineers  of  the  present  day. 

1.  In  order  to  enable  me  to  answer  the  first  of  the  above  questions 
relative  to  the  introduction  of  lenses  into  new  light-houses,  I  have 
obtained  from  M.  Frcsnel,  of  Paris,  a  detailed  estimate  of  the  ex- 
pense of  fitting  up  a  light-house  Avith  the  lens  apparatus,  including 
all  the  necessary  machinery  and  utensils,  and  on  the  scale  which  is 
in  use  at  the  magnificent  establishment  of  Cordouan. 

The  optical  part  consists  of  nine  lenses,  thirty  inches  in  diameter; 
nine  smaller  lenses,  with  their  reflectors,  for  widening  the  main 
beam  of  light;  and  another  piece  of  apparatus  for  collecting  the 
light  that  falls  below  the  lenses.  The  expense  of  this  part  of  the 
apparatus  is  1G,500  francs,  or  £687  10s. 


91 

The  mechanical  part  consists  of  all  the  frame  work  and  revolving 
apparatus,  with  three  Carcel  lamps.  The  expense  of  this  part,  in- 
cluding the  smaller  utensils,  is  9,500  francs,  or  £395 '16s.  Sd. — mak- 
ing the  total  amount  26,000  francs,  or  XI,  083  6s.  8d. 

Now,  the  expense  of  a  reflecting  apparatus  with  twenty-four  re- 
flectors is  <£1,387,  making  a  saving  of  £303  13s.  Qd.  in  favor  of  the 
lenses,  or  of  £413,  reckoning  £110  as  the  value  of  the  plate  glass 
in  the  lantern  for  lenses.  This  saving  will  be  increased  to  £513, 
because  £100  may  be  saved  by  substituting  an  invention  of  Mr. 
Oklham's  for  the  Carcel  lamps,  or  by  introducing  gas. 

If  these  twenty-four  reflectors  are  arranged  in  groups  of  six,  then 
the  brightest  light  which  at  any  one  time  reaches  the  eye  is  that  of 
six  reflectors,  which  is  repeated  four  times  in  each  revolution  ; 
whereas  in  the  lens  apparatus  we  have  a  light  equal  to  nine  reflect- 
ors, repeated  eight  times  during  each  revolution,  besides  the  ad- 
ditional light  of  the  eight  smaller  lenses,  and  that  of  the  other  piece 
of  apparatus.  Hence  it  is  demonstrable  that  the  lens  apparatus  is 
not  only  £413,  or  eventually  £513  cheaper  than  the  reflector  appa- 
ratus, but  gives  a  more  intense  and  penetrating  light. 

But,  independent  of  these  enormous  advantages,  the  lens  appa- 
ratus is  perennial,  while  the  other  is  perishable,  and  requires  to  be 
renewed. 

2.  In  answering  the  second  question,  respecting  the  propriety  of 
dismantling  every  light-house  in  Scotland,  and  substituting  lenses 
for  reflectors,  I  shall  treat  the  subject  commercially,  though  I  might 
at  once  solve  the  question  by  affirming,  that  if  the  lenses  afford,  as 
they  have  been  proved  to  do,  a  more  brilliant  and  penetrating  light, 
they  ought  to  be  instantly  adopted  from  motives  of  humanity,  even 
if  the  board  were  to  sustain  a  heavy  loss.  It  is  fortunate,  however, 
that  motives  of  economy  and  humanity  are,  in  this  case,  combined  in 
favor  of  the  change.  In  the  following  calculations  I  shall  take  a  fixed 
light,  such  as  that  of  the  Isle  of  May,  and  a  revolving  light,  similar 
to  that  of  the  Bell  Rock,  and  I  shall  suppose  that  the  apparatus  at 
both  these  stations  is  perfectly  new. 

The  Isle  of  May  light-house  has  twenty-seven  reflectors.  I  pro- 
pose to  substitute,  in  place  of  them,  a  lens  apparatus  which  will  cost 
£1,000,  the  sum  which  is  saved  by  there  being  no  revolving  ma- 
chinery being  sufficient  to  purchase  the  additional  lenses.  Now,  the 
twenty-seven  reflectors  at  present  used  will  produce  £567,  and  ] 
estimate  the  value  of  the  lamps,  &c.,  at  £50;  so  that  the  produce  of 


92 

the  present  apparatus  will,  at  the  very  least,  be  £617,  which,  taken 
from  .£1,000,  leaves  £383  as  the  expense  to  be  incurred  in  establish- 
ing the  new  system  of  light,  which  will  be  at  least  six  or  eight  times 
more  intense  than  those  now  in  use.  This  outlay,  however,  is  noth- 
ing when  we  come  to  consider  the  annual  saving. 

The  consumption  of  oil  per  annum  at  the  Isle  of  May  is  1,080  gal- 
lons, which,  at  six  shillings  per  gallon,  amounts  to  £324.  But  the 
lens  apparatus  requiring  only  one  lamp,  which  consumes  oil  equal  to 
fourteen  Argand  burners,  (according  to  Mr.  Stevenson, )  will  burn 
only  five  hundred  and  sixty  gallons  of  oil,  which  amounts  to  £168. 
Hence  there  will  be  an  annual  saving  in  oil  alone  of  £156,  besides 
£10  more  for  glass  chimneys  and  other  articles.  This  annual  saving 
of  £166  will  surely  justify  the  commissioners  in  making  an  outlay  at 
the  Isle  of  May  of  £383. 

If  we  now  take  a  revolving  light  of  24  reflectors,  like  that  of  the 
Bell  Rock,  the  advantage  of  changing  it  for  lenses  will  be  equally 
clear.  The  expense  of  the  largest  and  most  complete  lens  apparatus  for 
a  revolving  light,  like  that  of  Cordouan,  as  already  in  detail,  is  £1, 083. 
The  value  of  the  silver  in  the  24  reflectors  Avill  be  £504,  which,  with 
£45  for  lamps.  <fec.,  makes  £594,  leaving  an  outlay  of  only  £434  in 
order  to  give  the  Bell  Rock  light-house  a  scientific  and  an  efficient 
system  of  lights,  which  will  be  seen  at  a  much  greater  distance  than 
the  present  ones,  and  through  a  hazy  atmosphere,  which  will  com- 
pletely obstruct  the  lights  now  in  use. 

But  this  change  will  also  produce  a  great  annual  saving.  Twenty- 
four  reflectors  consume  960  gallons  of  oil,  which  will  cost  £288; 
whereas  the  lens  lamp  will  consume  only  560  gallons,  which  will  cost 
£168 — so  that  there  will  be  an  annual  saving  in  oil  alone  of  £120,  or 
£130  including  a  saving  in  glasses  and  other  articles.  In  reference 
to  the  economy  of  light-houses  furnished  with  lenses,  I  may  state  to 
the  board,  on  the  authority  of  M.  Fresnel,  the  highly  important  and 
startling  fact  that  the  annual  expense  of  the  great  light-house  of 
Cordouan,  including  light-house-men's  wages,  oil,  wicks,  Ac.,  is  £395 
6s.,*  while  the  Bell  Rock  light-house  costs  the  country  £861  annual- 
ly, on  an  average  of  four  years,  and  the  smaller  one,  at  Tarbetness, 
£555  annually,  on  an  average  of  three  years. 

3.  I  come  now  to  the  question  of  the  substitution  of  gas  for  oil. 
In  January,  1826,  more  than  seven  years  ago,  I  urged  the  commis- 

0  Lees  than  $1,800  per  annum  for  CorJuan  light,  fitted  with  a  first-order  lens. 


93 

sioners  to  make  this  great  and  obvious  improvement— an  improve- 
ment as  valuable  in  point  of  economy  as  it  is  in  reference  to  bril- 
liancy of  illumination.  Experience,  on  a  great  scale,  has  already 
given  its  decision  on  this  subject.  Austria  has,  many  years  ago, 
lighted  up  with  coal  gas  the  great  light-house  of  San  Salvore,  on  the 
coast  of  Istria,  and  the  effect  of  the  gas  far  surpasses  that  from  oil 
lamps.  The  details  of  the  relative  expense  of  gas  and  oil  have  been 
published  by  Professor  Aldine;  but  I  shall  trouble  the  board  only 
with  the  grand  result: 

The  annual  expense  of  oil  lights  was 1,861  florins. 

The  annual  expense  of  gas  is 932       l; 

Making  a  saving  of. 929       ' ' 

Exactly  one-half  of  that  of  oil.  If  we  include  the  interest  on  the 
money  advanced  for  the  gas  apparatus,  which  was  400  florins,  the 
total  expense  for  gas  annually  is  1,332  florins,  leaving  still  a  saving 
of  529  florins,  or  nearly  one-third  of  the  expense  of  illumination  by 
oil. 

I  may  add,  also,  that  two  small  light-houses  at  Dantzic  are  fitted 
up  with  gas.  One  of  them  consists  of  a  parabolic  reflector  22  inches 
in  diameter,  and  the  other  one  of  17  inches  in  diameter.  Here,  as 
in  Istria,  the  introduction  of  gas  has  been  found  to  be  a  measure  of 
great  economy,  and  the  additional  brilliancy  of  the  lights  at  Dantzic 
was  so  great  that  the  inhabitants  of  Hela,  where  the  gas  was  first 
lighted,  attributed  the  brilliant  effect  to  a  great  fire  in  the  city. 

4.  Seven  years  ago  I  suggested  also  the  necessity  of  providing,  in 
every  light-house,  the  means  of  exhibiting  powerful  lights  in  cases  of 
great  emergency,  and  I  have  described,  in  my  printed  paper,  the 
means  by  which  this  can  be  done.  The  Drummond  light  is  obviously 
well  adapted  for  this  purpose,  when  placed  in  the  focus  of  a  lens,  * 
but  an  equally  efficacious  and  much  cheaper  substitute  for  occasional 
purposes  has  been  suggested  by  Mr.  Robinson,  namely,  the  burning 

0  I  need  not  mention  to  any  person  acquainted  with  optics,  that  in  the  bungled  experi- 
ments with  the  lens  and  Drummond  light,  on  Thursday,  the  21st,  and  Friday,  22d  March, 
the  lens  was  so  misplaced  that  the  brilliant  part  of  the  column  never  reached  the  eyes  of 
the  ppcctators,  who  saw  only  the  penumbra ;  otherwiee,  the  Drummond  light,  with  the 
lens,  would  have  greatly  exceeded  that  by  the  reflector.  To  prove  this  by  occular  demon- 
stration, the  two  lights,  at  a  moderate  distance,  should  be  thrown  into  a  room,  and  their 
radiative  intensities  actually  measured. 


94 

of  blue  and  red  lights.  I  lately  recommended  the  introduction  of 
these  lights  into  the  focus  of  the  lens;  and  the  board  will  recollect 
the  splendid  effect  which  was  there  produced  by  the  red  light — alight 
especially  fitted  for  penetrating  a  hazy  atmosphere.  The  use  of  such 
lights  is  impracticable  with  reflectors,  and  the  facility  and  effect  with 
which  they  can  be  used  with  lenses,  is  a  new  argument,  if  any  were 
wanted,  in  favor  of  the  latter. 

5.  During  the  late  discussions  in  the  House  of  Commons,  Sir  Ed- 
ward Codrington  pointed  out  the  disadvantages  to  seamen  of  numerous 
light-houses;  but  these  disadvantages  exist  only  when  the  lights  arc 
not  properly  distinguished  from  one  another.  Hence  it  becomes  a 
matter  of  the  highest  importance,  especially  when  light-houses  have 
become  numerous,  to  establish  a  well  matured  system  of  distinguish- 
ing lights.  The  methods  used  in  France  do  not  afford  a  sufficient 
number  of  palpable  distinctions.  The  use  of  colored  media,  or  of 
transparent  plates  that  produce  periodical  colors,  or  polarized  tints, 
present  us  with  the  best  means  of  supplying  this  desideratum.  Ex- 
periments in  which  I  have  been  long  engaged,  on  the  absorption  of 
light  by  solid  fluids  and  gases,  have  led  me  to  various  results,  which 
are  peculiarly  applicable  to  the  present  purpose.  I  have  in  this  way 
succeeded  in  impressing  upon  any  given  light  a  numerical  character 
which  no  change  can  take  from  it,  and  which  can  be  recognized  by 
looking  at  the  light  through  a  small  and  cheap  instrument  made  for  the 
purpose.  If  the  commissioners  should  desire  to  witness  the  effects 
of  this  and  other  methods  of  distinguishing  lights,  an  apparatus 
could,  with  the  assistance  of  Mr.  Addie,  be  easily  constructed.  But 
if  these  new  plans  should  not  meet  with  the  approbation  of  the  board, 
the  introduction  of  the  lens  illumination  will  furnish  ample  means  of 
obtaining  distinguishing  lights,  by  a  well  arranged  succession  of  light 
and  darkness. 

Before  concluding  this  letter,  permit  me  to  make  a  few  remarks  on 
the  proposal  to  erect  a  lens  apparatus  at  Inchkeith.  As  a  light-house 
of  the  first  order  is  not  required  at  this  station,  it  might,  under  or- 
dinary circumstances,  be  sufficient  to  replace  the  present  very  in- 
efficient apparatus  by  lenses  of  half  the  area  and  half  the  price  (vi«: 
£25  each)  of  the  largest,  and  to  employ  only  a  burner  of  two  wicks, 
which  is  equal  to  three  and  a  half  Argand  burners. 

This  apparatus  would  consume  only  one-fourth  of  the  oil  now  used 
by  the  seven  Argand  burners,  and  would  give  a  light  several  times 
more  intense.  Such  an  apparatus  would  cost  about  £500.  But  as  I 


95 

presume  it  to  be  the  object  of  the  board  to  erect  one  of  the  best  lens 
apparatus,  as  a  guide  for  their  future  proceedings,  I  earnestly  recom- 
mend to  them  to  have  the  apparatus  complete,  with  all  the  modern 
improvements,  and  especially  to  light  it  with  coal  gas.  The  expense 
of  the  gas  apparatus  will  be  paid  by  its  own  savings  in  a  few  years, 
and  that  of  the  lens  apparatus  will  not  greatly  exceed  £1,000.  But, 
whatever  was  its  cost,  it  would  be  creditable  to  the  metropolis  of 
Scotland,  and  most  useful  to  the  navigation  of  the  Frith  of  Forth, 
which  is  frequently  beset  with  fogs,  to  have  at  Inchkeith,  a  light- 
house of  the  first  order  in  point  of  magnitude,  and  of  the  highest 
character  in  point  of  science. 

I  have,  &c., 

D.  BREWSTER. 
To  J.  A.  MACONOCHIE,  Esq., 

Convener  of  the  Lens  Committee. 


Letter  from  Messrs.  Alexander  Mitcliel  &  Son. 

BELMONT,  QUEEXSTOWX,  CORK, 

July  31,  1851. 

DEAR  SIR  :  We  are  in  receipt  of  your  favor  of  26th  May,  with  the 
interesting  documents  enclosed  in  it,  and  have  much  pleasure  in 
replying  to  your  inquiries  respecting  the  screw-pile,  being  satisfied 
that  the  more  extensively  it  is  known  the  more  extended  will  be  its 
application.  All  the  engineers  of  any  standing  in  these  countries 
have  expressed  themselves  strongly  in  its  favor  ;  of  these  we  may 
mention  Messrs.  "Walker  and  Burgess,  Rendal,  Brunei,  Cubitt,  &c., 
&c.,  all  of  whom  have  adopted  it  in  foundations  where  the  ground 
was  penetrable  or  covered  by  the  water,  and  in  every  case  it  has 
proved  eminently  successful. 

The  screw-pile  light-houses  inspected  by  you  and  Lieut.  Bache, 
when  in  this  country,  are  all  standing  as  you  left  them,  in  perfect 
order,  no  repairs  having  been  necessary,  with  the  exception  of  paint; 
since  then,  some  others  have  been  erected  by  us.  In  the  year  1849, 
we  placed  a  screw-pile  light-house  in  Dundalk  bay  for  the  commis- 
sioners of  Irish  lights;  in  1850  we  laid  the  foundation  of  a  screw-pile 
light-house  on  the  Chapman-sand,  off  Sheerness,  for  the  Corporation 
of  the  Trinity  House,  London,  and  we  are  at  present  constructing  a 


06 

screw-pile  light-house  on  a  shoal  in  Cork  bay,  for  the  Irish  Light- 
house Board  :  all  of  which  we  hold  to  be  a  sufficient  reply  to  whatever 
may  have  been  urged  against  the  system. 

The  Dundalk  light-house  stands  on  nine  wrought-iron  piles  placed 
seventeen  feet  in  the  ground  ;  it  has  been  some  time  lighted,  and  is 
a  great  boon  to  that  rising  town.  The  Chapman-sand  light-house  is 
also  on  nine  wrought-iron  piles  placed  thirty-nine  feet  in  the  ground, 
and  the  superstructure  is  now  advancing  under  the  management  of 
the  engineers  of  the  Trinity  House,  Messrs.  Walker  &  Burgess. 

The  construction  of  the  Cork  light-house,  the  foundation  of  which 
is  now  laid,  lias,  with  the  exception  of  the  lantern,  been  entrusted 
to  us  by  the  Irish  Light-house  Board  ;  of  all  which  works  and  others 
of  still  greater  importance  you  will  shortly  have  ample  details,  with 
drawings,  from  a  small  volume  at  present  in  the  press,  some  copies 
of  which  we  shall  have  much  pleasure  in  forwarding  to  you  ;  but 
probably  the  most  severe  test  to  which  these  piles  have  been  sub- 
jected maybe  seen  in  three  beacons  placed  by  us  on  the  Kish,  Black- 
water,  and  Arklow  banks,  dangerous  shoals  ten  or  twelve  miles  off 
the  coast  of  Wicklow  and  Wickford. 

Each  beacon  consists  of  a  massive  wrought-iron  pile  of  great 
length,  surmounted  by  a  large  ball ;  and  although  depending  for  sup- 
port on  a  single  screw  at  their  base,  they  have  all  withstood  the 
storms  of  several  winters;  but  these  beacons  are  not  of  themselves  of 
much  importance,  having  been  placed  principally  for  the  purpose  of 
pointing  out  the  sites  of  future  light-houses. 

As  to  our  screw-moorings,  we  have  several  persons  constantly  em- 
ployed in  putting  them  down,  in  the  various  bays  and  harbors  of  the 
United  Kingdom  ;  they  being  now  preferred  in  these  countries  to  all 
other  moorings. 

With  regard  to  our  light-houses,  we  have  not  found  it  necessary 
to  make  any  material  alteration  either  in  their  principle  or  form, 
although  we  have  in  the  materials  used,  as  we  now  prefer  wrought 
iron  and  British  oak,  to  the  fir  timber  from  the  Baltic  formerly  em- 
ployed. Wrought-iron  piles  being  in  most  eases  especially  necessary 
by  reason-  of  the  various  descriptions  of  sea-worm  which  everywhere 
infest  our  coast.  Wood,  however,  is  more  economical,  and  may  be 
safely  used  where  the  piles  are  occasionally  open  to  inspection 
throughout  their  entire  length,  as  in  the  case  of  the  Fleetwood  and 
Maplin  Sand  light-houses. 

The  slight  vibration  occasionally  observed,  so  far  from  detracting 


97 

• 

from  their  strength,  really  renders  them  more  stable,  in  the  same 
manner  and  for  the  same  reason  that  springs  have  been  found  useful 
when  applied  to  heavy  wagons ;  sudden  shocks  being  thus  in  both 
cases  considerably  softened  and  rendered  comparatively  harmless  ;  of 
this  the  Small's  light-house,  now  standing  about  sixty  years,  is  a 
remarkable  example,  which,  together  with  the  objections  to  cast-iron 
in  sea  foundations,  and  other  matters  interesting  to  engineers,  you  will 
find  alluded  to  in  the  pamphlet  which  accompanies  this  letter. 

Wooden  piles  when  placed  in  fresh  water,  being  free  from  the 
attack  of  worms,  might  (should  economy  be  an  object)  be  employed 
with  advantage  to  support  light-houses  and  beacons  on  the  shoals  of 
lakes  and  rivers.  You  say  the  chief  objection  urged  by  those  op- 
posed to  screw-pile  foundations  are,  too  great  vibration,  excessive 
torsion,  and,  in  some  localities,  not  sufficient  stability  to  withstand 
the  force  of  the  elements  opposed  to  it.  Of  vibration  we  have  spoken 
already,  and  hold  that  it  is  in  no  way  injurious  where  not  so  great  as 
to  affect  the  light,  and  where  the  structure  is  placed  on  a  base  of 
sufficient  breadth.  If  by  torsion  be  meant  the  power  employed  in 
screwing  in  the  piles,  that  can  be  rendered  innoxious  by  giving  to 
the  screws  the  proper  form,  and  to  them  and  the  piles  strength  suffi- 
cient to  bear  the  twist ;  or,  should  a  rotary  vibration  of  the  house  be 
meant,  this  can  be  entirely  prevented  by  the  application  of  angle 
braces  between  the  outer  piles  as  shown  in  the  Belfast  and  Fleet- 
wood  light-houses. 

As  to  giving  to  such  structures  power  to  resist  the  elements,  that 
must  in  every  case  depend  on  the  judicious  application  of  materials 
of  sufficient  strength,  of  not  difficult  solution,  as  shown  in  the  suc- 
cess that  has  attended  all  our  works.  Some  attempt  has  also  been 
made  in  this  country  to  lessen  confidence  in  the  screw-pile,  by  assert- 
ing that  the  Minot's  Ledge  light-house,  destroyed  last  April,  was 
placed  on  screw-piles  ;  but  this  we  understand  to  be  a  mistake,  and 
would  gladly  have  your  authority  for  its  contradiction.  The  accident 
was  possibly  owing  to  screw-piles  not  having  been  used  in  the  con- 
struction, or  too  insufficient  breadth  of  base. 

We  shall,  also,  at  all  times  be  most  happy  to  give  you  any  infor- 
mation in  our  power  on  the  subject  of  these  works  with  which  we 
may  be  connected  j  and  should  the  presence  of  one  of  us  tend  in  any 
degree  to  the  more  extensive  adoption  of  the  screw  pile  or  mooring 
in  the  United  States,  our  junior  is  quite  prepared  to  pay  your  country 
a  visit. 

7 


98 
p 

It  now  only  remains  for  us  to  express  our  high  gratification  at  your 
appointment  as  secretary  to  this  most  important  commission,  and  to 
subscribe  ourselves  with  the  highest  respect. 

Your  obedient  servants, 

A.  MITCHELL  &  SON. 
THORNTON  A.  JENKINS,  Esq. 


GREAT  GEORGE  ST.,  WESTMINSTER, 

August  1,  1850. 

MY  DEAR  SIR:  I  have  carefully  examined  the  design  for  a  landing 
pier  at  Osborne,  in  the  Isle  of  Wight,  which  is,  in  my  judgment, 
well  suited  to  its  purpose,  as  embracing  lightness  and  elegance  of 
appearance  with  great  strength  and  firmness  of  construction,  at  the 
same  time  offering  the  least  possible  obstruction  to  the  rise  of  the 
tide  or  stroke  of  a  wave. 

These  advantages  are  obtained  chiefly  by  the  use  of  the  patent 
screw  piles  of  wrought  iron,  which  are  eminently  adapted  for  the 
erection  of  structures  of  this  kind,  affording,  as  they  do,  a  great  fa- 
cility of  execution,  and  in  matters  of  this  kind  especially,  of  which  I 
may  instance  the  pier  for  landing  of  passengers  and  goods,  driven 
into  the  surf  or  swashing  of  the  sea  at  Coustoun,  in  Ireland,  in  which 
(as  probably  it'  would  in  this  case)  the  pier  formed  the  staging  for  its 
own  construction.  I  am  very  much  in  favor  of  the  patent  screw, 
having  used  it  for  very  large  moorings  in  the  river  Mersey,  and  my 
son,  during  the  last  year,  built  a  large  railway  bridge  in  the  fens  of 
Lincolnshire,  founded  and  supported  entirely  on  screw  piles ;  and  I 
believe  they  have  been  extensively  used  by  Mr.  Bendel  for  the  con- 
struction of  piers  used  in  the  erection  of  the  great  Portland  break- 
water. Nor  can  I  conceive  anything  better  adapted  for  a  landing 
pier  at  Osborne,  than  a  well-framed  platform  of  good  timber,  sup- 
ported on  piles  of  wrought  iron  screwed  firmly  into  the  bottom  of 
the  sea  to  the  requisite  and  proper  depth  ;  and  were  I  about  to  erect 
a  pier,  I  should  certainly  adopt  the  same  mode  of  proceeding. 
I  am,  my  dear  sir,  yours  faithfully, 

W.   CUBETT. 
To  CHARLES  MANBY,  Esq., 

Secretary  Institution  Civil  Engineers,  London. 


99 


NOTES. 

During  the  summer  of  1850,  Mr.  Mitchell  laid  clown  a  screw-pile 
foundation  for  a  light-house  on  the  Chapman  sands,  near  the  mouth 
of  the  Thames.  These  piles,  nine  in  number  and  six  inches  in  diam- 
eter, were  screwed  down  forty  feet,  although  the  bottom  is  very- 
hard  ;  but  this  depth  was  demanded  by  the  contract.  The  heads  of 
the  piles  were  framed  together,  and  the  superstructure  is  to  be  com- 
pleted by  the  engineer  to  the  Trinity  House,  Mr.  James  Walker. 
Second,  Mr.  Mitchell  has  contracted  with  the  Trinity  House  to  put 
down  a  similar  foundation  for  another  light-house  on  the  Goodwin 
sands.  Third,  the  son  of  Mr.  Mitchell  was  employed  last  December 
in  erecting  a  screw-pile  light-house  at  the  entrance  of  Cork  Harbor, 
for  the  Irish  Ballast  board.  Fourth,  Mr.  Mitchell  has  been  called 
upon  for  estimates  to  erect  a  screw-pile  light-house  at  Singapore,  and 
also  for  a  viaduct  many  miles  in  length,  to  be  constructed  over  the 
marshes  in  the  province  of  Gararat,  (India,)  terminating  in  a  screw- 
pile  pier  for  shipping  cotton,  wool,  &c.  Fifth,  it  is  proposed  to  use 
2,500  screw  piles  on  the  Portland  breakwater.  These  form  a  viaduct 
on  which  the  cars  loaded  with  stone  from  the  quarries  are  made  to 
travel  by  steam  power.  The  stone  is  dumped  off  each  car  into  the 
water,  the  piles  being  thus  buried  up  in  the  operation.  The  great 
expedition  and  facility  obtained  by  the  use  of  this  screw-pile  viaduct 
or  railway  cannot  be  over  estimated,  as  the  train  is  loaded  at  the 
quarries  and  then  rapidly  drawn  to  the  place  of  deposit,  where  the 
trap  doors  in  the  bottom  of  the  cars  are  opened  and  the  whole  load 
discharged  in  a  few  minutes.  This  is  one  of  the  greatest  works  of 
modern  days. 


SCREW   MOORINGS. 

It  is  highly  desirable  that  these  useful  moorings  should  be  intro- 
duced for  securing  our  buoys— the  loss  and  repairs  of  which  cost  now 
annually  $20,000,  owing  to  the  insufficient  moorings  we  now  use  in 
the  shape  of  iron  or  stone  blocks  ;  a  large  number  of  buoys  are  swept 
away  every  year,  or  else  dragged  off  into  deep  water  or  out  of  true 
position.  The  adoption  of  this  mooring  is  general  in  Great  Britain 
and  the  north  of  Europe. 


100 


Report  on  the  Lightning  tiods  of  Light-houses. 

SEPTEMBER  25,  1843. 

The  undersigned  have,  according  to  their  instructions,  met  and 
considered  the  circumstances  under  which  light-houses  are  placed  as 
respects  lightning,  and  have  arrived  at  the  following  conclusions: 

That  light-houses  should  be  well  defended  from  the  top  to  the 
bottom ; 

-   That  as  respects  the  top,  the  metal  of  the  lantern  and  upwards  is 
sufficient  to  meet  every  want  and  satisfy  every  desire  and  fear; 

That  for  the  rest  of  the  courses  down  the  tower,  a  copper  rod 
three-fourths  of  an  inch  in  diameter  is  quite  and  more  than  sufficient; 

That  at  the  bottom  where  the  rod  enters  the  earth,  it  is  desirable 
at  its  termination  to  connect  it  metallically  with  a  sheet  of  copper 
three  or  four  feet  long  by  two  feet  or  more  wide  ;  the  latter  to  be 
buried  in  the  earth  so  as  to  give  extensive  contact  with  it; 

That  glass  repellers  are  in  every  case  useless; 

That  glass  thimbles  are  not  needed,  but  do  no  harm; 

That  if  the  repeller  be  removed,  and  the  joint  on  the  vane  be  ter- 
minated as  the  lightning-rods  usually  are,  and  then  the  metal  of  the 
lantern  be  strongly  attached  to  and  cemented  with  the  upper  end  of 
the  copper  rod,  and  the  rod  continued  down  the  tower  to  the  earth, 
and  the  sheet  of  copper  buried  in  it,  such  a  system  will  be  an  effec- 
tual and  perfectly  safe  lightning  conductor; 

That  then  there  need  be  no  rod  end  rising  by  the  side  of  and  above 
the  lantern; 

That  the  rod  may  (if  required  on  other  accounts)  come  down  on 
the  inside  of  the  building  or  in  a  groove  in  the  wall,  but  should  not 
be  unnecessarily  removed  from  observation  and  inspection; 

That  all  large  metallic  arrangements  in  the  stone  work  in  other 
non-metallic  parts  of  the  tower  of  the  light-house,  such  as  tying  bars, 
metal  flues,  &c.,  should  be  well  connected  by  copper  Avith  the  con- 
ductor; 

That  the  vicinity  of  two  metallic  masses,  without  contact  or  metal- 
lic communication,  is  to  be  avoided; 

That  as  to  the  South  Foreland  high  light,  the  lantern,  the  central 
stone,  and  the  copper  rod  proceeding  from  it  to  the  earth,  connected 
as  they  now  are,  form  a  perfect  lightning  conductor,  even  without 
the  rod  that  is  there  erected;  but, 


101 

That  it  is  important  casual  arrangements  should  never  be  depended 
upon  for  lightning  conductors,  but  a  copper  rod  be  established  for  the 
especial  purpose ;  for  if  the  former  be  trusted  to,  the  carelessness  or 
ignorance  of  workmen  may,  at  after  periods  upon  occasions  of  repair 
or  cleansing,  cause  the  necessary  metallic  connection  to  be  left  imper- 
fect or  incomplete,  and  then  the  arrangement  is  not  merely  useless 
but  dangerous. 

That  as  to  the  Eddystone,  it  is  desirable  to  connect  the  system  of 
wrought-iron  ties  in  it  with  the  lightning  conductor,  by  joining  the 
lower  part  of  that  iron  rod  which  is  nearest  to  the  conductor,  with  the 
latter  by  a  copper  rod  or  strap,  equivalent  to  the  conductor  in  sec- 
tional area. 

That  the  Dungeness  light-house  is  in  a  very  anomalous  condition; 
to  rectify  which  the  two  repellers  should  be  removed,  and  also  the 
representative  of  the  top  of  a  lightning  rod  attached  to  the  flue;  and 
that  then  a  good  copper  conductor  should  be  attached  to  the  metal  of 
the  lantern,  upon  the  principles  already  expressed. 

M.  FARADAY. 

JACOB  HERBERT,  Esq.,  &c.,  &c. 


Extract  from  minutes  of  the  Board,  held  on  the  26th  September,  1843. 

Read  a  report  from  Professor  Faraday  on  the  reference  made  to 
himself  and  Mr.  Walker,  on  the  subject  of  the  construction  of  light- 
ning conductors  for  light-houses. 

Read,  also,  a  letter  from  Mr.  Walker,  conveying  his  approval  of 
all  that  Mr.  Faraday's  report  contains,  and  satisfactorily  explaining 
the  grounds  on  which  he  has  not  thought  it  right  to  sign  the  report. 
The  board  having  hereupon  considered  and  approved  the  suggestions 
offered  in  the  said  report,  ordered  that  Mr.  Walker  be  instructed  to 
cause  the  light-houses  belonging  to  the  corporation  to  be  protected  by 
the  means  recommended  by  Mr.  Faraday,  and  in  which  he  expressed 
his  entire  concurrence  as  above  said;  and  that  Mr.  Faraday  be  ac- 
quainted therewith. 


IRISH  LIGHTS. 

Extract  from  Senate  Document  No.  488,  1st  session,  2Sth  Congress. 

In  light-houses,   especially  fixed  lights,  where  any  considerable 
portion  of  the  circle  is  to  be  illuminated,  say  exceeding  one  half,  (or 


102 

more  than  180°,)  refractors  should  be  chosen,  as  light  can  with  them 
be  more  economically  used.  There  is,  also,  thus  a  more  equal  dif- 
fusion of  the  light  around.  In  small  harbor  lights  where  an  angle  of 
only  a  few  degrees  is  to  be  lighted,  as  in  marking  a  channel,  it  will 
be,  in  most  cases,  found  advantageous  to  use  reflectors. 

The  general  number  of  keepers  to  each  light-house  is  two;  a  prin- 
cipal and  an  assistant  keeper.  There  are  only  two  light-house  sta- 
tions on  the  coast  of  Ireland  in  which  there  are  three  keepers  to 
each;  those  are  on  tidal  rocks,  having  shore  establishments. 

The  annexed  document  (in  reply  to  No.  3)  states  the  number  of 
persons  in  each  light-vessel,  and  the  arrangement  for  relief. 

Buoys  are  distinguished  by  differences  of  color,  as  black,  red,  <fcc., 
or  any  of  these,  Avith  broad  paralleled  or  diagonal  belts  of  different 
colors,  and  by  affixed  beacons  of  different  forms. 

Light-vessels  are  moored  by  single  anchors ;  (iron  mushrooms  from 
one  and  a  half  to  two  tons  weight.)  The  chains  are  from  one  and 
three  quarters  to  two  inches  in  diameter,  of  iron,  with  studs  or  cross- 
bars. Stone  sinkers  are  generally  used  for  buoy  moorings ;  they 
weigh  from  twenty  to  thirty  hundred  weight  each,  according  to  the 
size  of  buoys.  The  chains  are  from  one  inch  to  one  and  a  half  inch 
in  diameter,  of  iron,  without  studs.  Mushroom  anchors  were  for- 
merly used  for  mooring  buoys,  but  stone  sinkers  are  found  to  be  as 
effective  (when  the  buoy  alone  is  to  be  secured)  and  are  not  more 
than  one -eighth  the  cost. 

Weather  being  favorable,  the  length  of  time  usually  occupied  in 
putting  down  one  of  Mitchell' s  screw  moorings  for  a  mooring-buoy  is 
from  three  to  four  hours.  A.  strong  raft,  having  a  central  opening, 
is  best  adapted  for  working  the  capstan,  shears,  &c. ;  but  two  floats 
or  buoys,  platformed  over,  lashed  together,  securely  moored  and 
well  steadied  with  quarter-lines,  form  a  ready  and  serviceable  sub- 
stitute. 

The  ballast  board  have  several  of  these  screws  in  use  at  Dublin, 
and  propose  using  them  more  extensively,  both  as  moorings  and  as 
bases  for  beacons.  Considered  as  moorings  for  one  or  many  vessels, 
although  taking  the  mere  weight,  they  are  necessarily  more  costly 
than  ordinary  moorings,  yet,  bringing  into  account  their  much  greater 
power  of  holding,  (in  all  places  suitable  to  their  use,)  they  would 
become,  perhaps,  the  most  economical  that  could  be  adopted. 

Time  will  not  now  permit  me  to  attempt  arranging  the  foregoing 
list  of  replies  more  methodically  or  more  in  detail.  The  report 


103 

which  it  is  expected  will  shortly  be  published  by  order  of  the  select 
committee  of  the  House  of  Commons  will  contain  any  further  details 
that  might  be  wished.  GEORGE  HA.LPIN,  C.  E. 

DUBLIN,  October  27,  1845. 


Return  to  an  order  of  the  Honorable  the  House  of  Commons,  dated  \±th 
August,  1846. 

A  return  by  the  corporation  of  Trinity  House  of  Deptford  Strond, 
showing  whether  they  have  adopted  the  recommendation  of  the 
select  committee  on  light-houses  in  the  use  of  colza,  or  rapeseed 
oil,  instead  of  sperm  oil,  and  what  saving  of  expense  has  accrued 
therefrom;  and  also  whether  they  have  made  any  and  what  reduc- 
tion in  the  light  dues  charged  by  them. 

RAPESEED   OIL. 

The  attention  of  the  corporation  of  Trinity  House  had  been  drawn 
to  rapeseed  oil  as  a  substitute  for  sperm  oil,  and  trials  of  its  qualities, 
with  the  object  of  introducing  it  into  use  at  their  light-houses  and 
light-vessels,  had  been  directed  to  be  made  prior  to  the  sitting  of 
the  select  committee  on  light-houses,  in  1845. 

Suitable  arrangements  for  the  burning  of  this  oil  have  since  been 
made  and  are  continued  as  opportunities  present  themselves,  and  its 
use  will  probably  become  general  at  the  light-house  and  light-vessel 
stations  in  England.  The  quantity  which  was  contracted  for  and 
supplied  in  the  spring  of  the  year  1841  was  thirty  tuns,  being  so 
much,  or  nearly  so,  in  diminution  of  the  contract  quantity  of  sperm 
oil,  the  respective  contract  prices  being,  for  rapeseed  oil,  3s.  9d.  per 
imperial  gallon ;  spermaceti  oil,  6s.  4d.  per  imperial  gallon.  It  must 
not,  however,  be  supposed  that  the  whole  difference  in  the  price  per 
imperial  gallon  is  actually  saved,  because  the  quantity  of  rapeseed 
oil  consumed  very  considerably  exceeds  that  of  spermaceti  oil,  if  the 
flame  in  the  lamp  be  maintained,  as  it  should  be,  at  the  maximum  of 
its  power. 

The  time  which  has  elapsed  since  the  use  of  this  oil  has  been  ex- 
tended has  not  been  sufficient  to  show  conclusively  what  the  excess 
of  consumption  will  be  in  practice;  but  the  present  results  induce 
the  expectation  that  it  will  be  very  considerable,  and  there  do  not,  at 


104 

this  time,  appear  any  certain  grounds  for  supposing  that  the  differ- 
ence can  be  materially  reduced. 

In  the  autumn  of  1845  the  board  referred  the  investigation  of  the 
power  and  qualities  of  the  light  produced  from  the  combustion  of 
this  description  of  oil  to  Professor  Faraday,  and  the  following  valu- 
able and  interesting  observations,  having  reference  to  the  question 
of  consumption,  are  extracted  from  his  consequent  report,  dated  the 
9th  day  of  October  of  that  year,  viz:  "Having  burnt  the  lamp  for 
many  days,  I  have  been  much  struck  by  the  great  steadiness  of  the 
rape  oil  lamps,  either  considered  alone  or  as  compared  with  the 
sperm  oil  lamps.  They  would  burn  for  twelve  or  fourteen  hours  at 
a  time,  with  little  or  no  alteration  of  the  light,  the  cottons  or  lamps 
not  being  touched  the  whole  time  ;  whereas  the  sperin  oil  lamps 
would,  in  the  course  of  four,  five,  or  six  hours,  give  a  diminished 
flame,  from  the  incrustation  of  the  charred  part  of  the  cotton  retard- 
ing the  flow  of  oil.  In  the  rape  oil  lamps  the  coal  is  broken  and 
porous,  and  serves  for  wick  almost  as  well  as  the  fresh  cotton ;  but 
in  the  sperm  oil  lamp  the  coal  forms  a  hard,  continuous  ring,  which 
seals*  up  the  ends  of  the  threads;  and  this,  with  the  more  confined 
condition  of  the  burner,  and  the  greater  distance  of  the  oil  beneath, 
(from  intentional  difference  of  flow  in  the  lamp,)  causes  the  sperm 
oil  lamp  flame  to  fall  in  brightness,  and  requires  that  the  wick  should 
be  retrimmed.  Several  causes  conspire  to  this  hard  condition  of 
the  charred  cotton,  which  I  need  not  enter  into  here. 

"I  have  made  many  careful  experiments  on  the  proportion  of  light 
produced  by  the  two  kinds  of  lamps,  in  every  case  weighing  the  oil 
before  and  after  combustion,  so  as  to  know  exactly  the  quantity 
burnt;  and  making,  during  the  experiments,  above  a  hundred  com- 
parisons of  the  lights,  one  with  another.  The  rape  oil  lamps  were 
always  more  brilliant  than  the  sperm  oil  lamps,  except,  indeed,  in  one 
or  two  rare  cases;  but,  at  the  same  time,  more  oil  was  burnt  in  them. 
The  observations  were  made  numerous,  that  the  errors  in  the  percep- 
tion of  the  eyes  might  compensate  each  other.  In  each  particular 
experiment  it  was  evident  that  the  light  was  nearly  in  the  proportion 
of  the  oil  burnt;  and  upon  making  a  comparison  of  all  the  results, 
the  following  conclusion  was  obtained:  From  one  hundred  and  eight 
observations  of  the  lights,  taken  at  such  times  as  appeared  fitted  to 
give  the  best  mean  expression  of  the  light  of  the  lamps,  compared 
with  the  oil  burnt  in  them,  the  average  light  of  the  rape  oil  lamp  came 


105 

out  as  one  and  a  half,  that  of  the  sperm  oil  being  one.  This  is  the 
mean  result  of  the  light  involved  by  the  lamps  burning  for  the  same 
period  of  time.  On  summing  up  the  amount  of  oil  burnt  in  the  same 
time,  it  gave  almost  exactly  the  same  proportion;  for  the  oil  con- 
sumed in  the  sperm  lamps  being  1,  that  consumed  in  the  rape  oil 
lamps  was  1.505.  I  have  considerable  confidence  in  this  result,  the 
quantity  of  oil  consumed  being  several  gallons,  and  the  observations 
of  the  light  very  continuous  and  numerous." 


Supplementary  return  to  an  order  of  the  honorable  House  of  Commons, 
dated  August  14,  1846. 

"Statements  by  the  corporation  of  the  Trinity  House  of  Deptford 
Strond,  by  the  ballast  board  in  Dublin,  and  by  the  commissioners  of 
Northern  lights,  showing  whether  they  have  adopted  the  recommend- 
ation of  the  select  committee  on  light-houses,  on  the  use  of  colza  or 
rapeseed  oil,  instead  of  sperm  oil,  and  what  saving  of  expense  has 
accrued  therefrom;  and  also  whether  they  have  made  any,  and  what 
reduction,  in  the  light  dues  charged  by  them  respectively." 

Ordered  by  the  House  of  Commons  to  be  printed,  18th  March,  1847. 


Return  by  the  Commissioners  of  Northern  Light-houses. 

1.  Whether  they  have  adopted  the  recommendation  of  the  select 
committee  on  light-houses,  in  the  use  of  colza  or  rapeseed  oil,  instead 
of  sperm  oil,  and  what  saving  of  expense  has  accrued  therefrom  ? 

On  the  10th  January  last,  the  engineer  of  the  board  reported  on  this 
subject  to  the  commissioners,  in  the  following  terms:  "At  the  sug- 
gestion of  Mr.  Hume,  M.  P.,  chairman  of  the  light-house  committee, 
I  have  obtained  from  Messrs.  Wilkins,  of  Long  Acre,  a  sample  of  an  oil 
going  under  the  name  of  oil  of  colza,  but  in  no  respect  characterized 
by  the  peculiarities  which  marked  the  colza  oil  of  the  French  light- 
houses. This  oil  is  burned  in  a  lamp  with  a  chimney  indented  at  the 
flame  by  means  of  a  deep,  narrow  groove  on  its  outside,  which  seems 
to  be  the  same  as  that  which  is  used  in  what  is  called  the  solar  lamp, 
and  is  now  oddly  enough  termed  the  catoptric  lamp.  The  oil  is  said 
to  be  nearly  fifty  per  cent,  cheaper  than  spermaceti,  but  is  gen- 


106 

erally  held  to  be  more  rapidly  consumed.  I  have  made  several  trials 
of  the  colza  and  the  sperm  oil  in  burners  of  different  kinds,  with 
somewhat  contradictory  results,  both  as  regards  brilliancy  of  effect 
and  durability.  I  am  not,  therefore,  prepared  to  offer  any  very  pre- 
cise information  as  to  the  result  of  my  inquiry.  It  appears  to  me, 
however,  that  I  may  safely  enough  state  that  the  colza  oil  is  some- 
what more  rapidly  consumed  where  an  equally  dense  light  is  evolved, 
and  its  flame  generally  seems  to  contain  a  greater  proportion  of  the 
orange  color,  which  marks  imperfect  combustion. 

"The  adoption  of  this  oil  would  involve  an  entire  remodeling  of 
the  burners,  so  as  to  admit  of  thicker  wicks,  and  would  probably 
lead  to  an  enlargement  of  the  cellars,  so  as  to  receive  a  larger  sup- 
ply. I  conclude,  therefore,  that  during  the  present  season  the  com- 
missioners would  not  be  warranted  in  doing  more  than  to  make  trial 
of  a  cask  or  two  of  this  oil  at  a  dioptric  and  a  catoptric  light.  I  may 
add,  that  other  reasons  for  proceeding  somewhat  cautiously  in  regard 
to  the  colza  oil  may  be  found  in  the  uncertainty  as  to  the  source  of 
supply,  and  the  absence  of  all  experimental  knowledge  of  the  effect 
of  cold  in  causing  it  to  become  thick." 

The  suggestions  in  this  report  having  been  approved  by  the  board, 
a  supply  of  the  oil  has  been  sent  to  several  of.  the  stations;  but  the 
result  has  not  as  yet  been  reported  to  the  board. 


A  return  by  the  Commissioners  of  Northern  Light-houses,  relative  to  the 
substitution  ofrapeseed  oil  for  sperm  oil,  and  the  saving  that  has  accrued 
therefrom. 

To  the  first  head  of  the  preceding  order,  "Whether  they  have 
adopted  the  recommendation  of  the  select  committee  on  light-houses 
in  the  use  of  colza  or  rapeseed  oil,  instead  of  sperm  oil,  and  what 
saving  of  expense  has  accrued  therefrom?"  the  commissioners,  in 
making  a  return  to  this  order  (presented  to  the  House  26th  August, 
1847,  Vetis  No.  2)  stated,  that  "a  supply  of  the  oil  has  been  sent  to 
several  of  the  stations,  but  the  result  has  not  as  yet  been  reported 
to  the  board." 

On  9th  January  last  the  engineer  submitted  a  further  interior 
report  to  the  board,  a  copy  of  which  is  appended  hereto  (No.  1.) 

The  engineer  having  on  the  10th  instant  reported  to  the  board  the 


107 

result  of  the  trials  of  the  oil  in  question,  the  same  is  now  submitted 
as  a  supplementary  return  to  the  order  of  the  honorable  House,  and 
is  hereto  appended  (No.  2.) 

By  order  of  the  board, 

ALEX.   CUNNINGHAM,  Secretary. 
NORTHERN  LIGHTS  OFFICE, 

Edinlurg,  March  13,  1847. 


Excerpt  from  annual  report  by  Mr.  Alan  Stevenson,  Engineer  to  the  Com- 
missioners of  Northern  Light-houses,  dated  $th  January,  1847. 

The  trials  of  the  colza  oil  alluded  to  last  year,  as  suggested  by  Mr. 
Hume,  M.  P.,  late  chairman  of  the  light-house  committee  in  1845, 
have  just  been  commenced,  and,  in  so  far  as  the  reports  from  the  sta- 
tions have  been  received  of  the  preliminary  experiments  there  is 
reason  to  believe  that  this  oil  will  answer  in  light-houses.  The  ques- 
tion of  the  relative  expense  of  the  colza  and  spermaceti  oils,  how- 
ever, must  remain  undecided  until  further  trials  shall  have  been  made; 
and  longer  experience  is  also  desirable,  in  order  to  show  in  what 
manner  the  oil  is  acted  upon  by  frost.  The  stations  fixed  upon  for 
the  trials  are  Inchkeith,  Isle  of  May,  Kinnaird's  Head,  Corswall, 
Little  Ross,  and  Calf  of  Man,  three  being  dioptric  and  three  reflect- 
ing lights. 


The  report  of  Alan  Stevenson,  engineer. 

EDINBURGH,  March  10,  1847. 

In  my  last  annual  report  on  the  state  of  the  light-houses,  I  directed 
the  attention  of  the  board  to  the  propriety  of  making  trial  at  several 
stations,  of  the  patent  colza  or  rapeseed  oil  prepared  by  Messrs. 
Briggs,  of  Bishopsgate  street.  These  trials  have  now  been  made 
during  the  months  of  January  and  February,  at  three  catoptric  and 
three  dioptric  lights,  and  the  results  have  from  time  to  time  been 
made  known  to  rne  by  the  light-keepers,  according  to  instructions- 
issued  to  them,  as  occasion  seemed  to  require.  The  substantial 
agreement  of  all  the  reports  as  to  the  qualities  of  the  oil,  renders  it 
needless  to  enter  into  any  details  as  to  the  slightly  varying  circum- 
stances of  each  case,  and  I  have  therefore  great  satisfaction  in  briefly 


108 

stating  as  follows  the  very  favorable  conclusions  at  which  I  have 
arrived : 

1.  The  colza  oil  possesses  the  advantage  of  remaining  fluid  at  tem- 
peratures which  thicken  the  spermaceti  oil,  so  that  it  requires  the 
application  of  the  frost-lamp. 

2.  It  appears  from  pretty  careful  photometrical  measurements  of 
various  kinds,  that  the  light  derived  from  the  colza  oil  is,  in  point  of 
density,  a  little  superior  to   that  derived  from  the  spermaceti  oil, 
being  in  the  ratio  of  1.056  to  1. 

3.  The  colza  oil  burns  both  in  the  Fresnel  lamp  and  the  single 
Argand  burner  with  a  thick  wick,  during  seventeen  hours,  without 
requiring  any  coaling  of  the  wick  or  any  adjustment  of  the  damper; 
and  the  flame  seems  to  be  more  steady  and  free  from  flickering  than 
that  from  spermaceti  oil. 

4.  There  seems  (most  probably  owing  to  the  greater  steadiness  of 
the  flame)  to  be  less  breakage  of  glass  chimneys  with  the  colza  than 
with  the  spermaceti  oil. 

5.  The  consumption  of  oil,  in  so  far  as  that  can  be  ascertained, 
during  so  short  a  period  of  trial,  seems  in  the  Fresnel  lamp  to  be  121 
for  colza,  and  114  for  spermaceti;  while  in  the  common  Argand,  the 
consumption  appears  to  be  910  for  colza,and  902  for  spermaceti. 

6.  If  we  assume  the  mean  of  these  numbers,  515  for  colza  arid  508 
for  spermaceti,  as  representing  the  relative  expenditure  of  these  oils, 
and  if  the  price  of  colza  be  3s.  9cZ.,  while  that  of  spermaceti  is  6s.  9rf. 
per  imperial  gallon,  we  shall  have  a  saving  in  the  ratio  of  1  to  1.775, 
which,  at  the  present  rate  of  supply  for  the  northern  lights,  would 
give  a  saving  of  about  .£3,266  per  annum. 

Of  these  conclusions,  the  three  last  may  be  considered  as  more  or 
less  conjectured,  being  founded  on  data  derived  from  too  short  a  trial; 
but  the  striking  agreement  of  the  results  obtained  at  the  six  lights 
in  which  the  experiments  were  made,  tend  in  some  measure  to  supply 
the  place  of  a  longer  period  of  trial;  and  I  have  no  hesitation,  there- 
fore, in  recommending  the  board  at  once  to  introduce  the  use  of  the 
colza  oil  into  all  the  dioptric  lights,  except  that  of  Lhe  Skerry  vore,  where 
some  special  reasons  induce  me  to  defer  the  change  for  another  sea- 
sou.  In  the  catoptric  lights,  the  only  reason  for  not  making  an  equally 
extensive  trial  is  the  necessity  for  renewing  all  the  burners,  which 
require  to  be  so  constructed  as  to  receive  thick  wicks  of  brown  cot- 
ton; and  it  may  perhaps  be  considered  prudent  to  proceed  with  some 
caution  in  changing  the  apparatus  so  as  to  suit  for  burning  a  patent 


109 

oil,  the  circumstances  attending  the  regular  and  extensive  supply  of 
which  are  not  yet  fully  known.  I  may  remark,  that  I  have  burnt  the 
colza  oil  in  the  solar  lamp  alluded  to  in  my  last  report;  but  I  disap- 
prove of  it  as  tending  to  elongate  the  flame  vertically,  and  thus  to 
decrease  its  horizontal  volume.  The  elongated  form  of  flame  increases 
the  divergence  vertically  when  the  light  is  lost,  and  so  far  circum- 
scribes its  horizontal  range  where  it  is  most  required.  I  have,  there- 
fore, substituted  the  thick  wick  burner  for  the  solar  lamp,  whereby 
an  equally  complete  combustion  is  obtained,  and  the  proper  form  of 
the  flame  is  at  the  same  time  preserved. 
To  the  BELL  ROCK  COMMITTEE. 


Letter  from  W.  C.   Wilkins,  Esq. 

LONDON,  July  IS,  1850. 

SIR:  In  answer  to  your  letter  of  29th  of  May,  requesting  informa- 
tion concerning  improvements  in  light-houses  and  light-vessels,  I  beg 
herewith  to  enclose  a  book  which  I  have  recently  published  contain- 
ing drawings  and  particulars  of  the  various  catadioptric  light  appaj 
ratus  on  Fresnel's  system,  used  in  this  country,  including  two  appa 
ratus  for  which  I  have  obtained  letters  patent  in  connection  with  M. 
Letourneau,  of  Paris;  one  is  a  revolving  light,  short  eclipses  produced 
by  a  new  arrangement  of  the  lenses,  of  the  central  part  and  additional 
vertical  prisms,  gathering  the  rays  from  the  upper  and  lower  catadi- 
optric portions,  giving  a  great  increase  of  light,  and  is  what  I  am 
now  exhibiting  in  the  great  crystal  palace,  Hyde  Park;  the  other  is 
a  reciprocating  apparatus,  with  additional  vertical  prisms  before 
mentioned,  and  reduce  the  cost  of  flashing  light  when  it  is  not 
required  to  be  seen  beyond  the  same  circle,  or  half  the  horizon. 

I  have  also  effected  great  improvements  in  revolving  floating  lights 
by  placing  the  machinery  below  the  deck,  thereby  avoiding  the  lia- 
bility to  injury,  and  producing  a  better  action.  I  have  enclosed 
circulars  of  these  novelties,  to  assist  in  conveying  the  idea  of  their 
advantage  to  you. 

In  reply  to  the  latter  sentence  of  your  letter,  seeking  intelligence 
respecting  the  oils,  I  beg  to  say  that  the  colza  or  rapeseed  oil  is  in 
constant  use  here;  it  has  quite  superseded  sperm,  and  with  suitably 


110 

constructed  lamps,  wicks,  <fec.,  gives  a  better  light  and  is  more  eco- 
nomical. (I  shall  be  happy  to  supply  you  with  a  sample.)  After  it 
has  been  pressed  from  the  seed  it  is  purified  by  a  patent  process, 
which  is  of  course  secret — known  only  to  the  parties  who  manufac- 
ture it;  the  price  averages  about  3s.  Wd.  per  gallon,  but  fluctuates 
according  to  the  demand.  Numerous  experiments  have  been  tried 
under  the  direction  of  Professor  Faraday,  and  he  considered  the 
rapeseed  oil  as  superior  to  all  others  for  the  purpose  of  illuminating 
light-houses,  &c. 

Trusting  that  this  will  meet  your  approval  and  contains  what  you 
wish  to  know,  and  that  I  may  be  honored  with  your  future  com- 
mands, which  shall  always  have  my  best  attention, 

I  am,  sir,  your  most  obedient  servant, 

W.  C.  WILKLVS. 

Lieut.  T.  A.  JENKINS,  U.  S.  N., 

Secretary  to  Light-house  Board,   Washington. 


REFUGE    BUOY-BEACON. 


The  ordinary  buoys  in  use  on  the  English  coast  and  elsewhere,  for 
pointing  out  the  position  of  dangerous  shoals  and  sand  banks,  are  of  a 
conical  form,  made  chiefly  of  wood,  and  hooped  like  a  cask,  being 
moored  with  the  apex  or  sharp  end  downwards;  and,  owing  to  this 
shape,  in  a  strong  tide-way  and  heavy  sea  they  are  at  times  nearly 
pulled  under  water,  tugging  with  an  immense  strain  upon  their 
moorings,  and  frequently  breaking  adrift  at  the  very  time  when 
most  required;  moreover,  from  their  construction,  they  twist  and 
twirl  so  as  to  render  them  impossible  of  approach  or  refuge  for  sav- 
ing life  in  case  of  shipwreck.  Captain  George  Peacock,  the  super- 
intendent and  dockmaster  of  the  Southampton  docks,  has  invented  a 
new  kind  of  mark-buoy,  or  floating-beacon,  which,  from  its  peculiar 
form  and  construction,  and  the  manner  in  which  it  is  moored,  rises 
over  the  crest  of  the  waves  in  the  heaviest  gales  and  strongest  tide, 
and  is  not  acted  upon  like  the  ordinary  buoy;  it  is,  in  fact,  capable 
of  holding  from  ten  to  twelve  persons  with  ease  in  case  of  contiguous 


Ill 

shipwreck,  and  of  affording  them  a  safe  temporary  asylum— it  being 
in  fact  at  once  a  buoy,  beacon,  and  life-boat,  and  the  cost  of  it 
scarcely  exceeds  that  of  the  ordinary  buoys  now  in  use. 

The  plan  and  model  having  been  approved  of  by  the  pier  and  har- 
bor commissioners  of  Southampton,  one  of  these  buoy-beacons  was 
laid  down  off  the  Spit,  at  Calshot  Castle,  on  the  12th  of  August  last, 
and  has  withstood  the  whole  of  the  severe  gales  of  the  last  six 
months  without  showing  the  least  symptom  of  injury  or  leakage. 

The  hull,  which  is  of  sheet  iron,  is  of  a  semi-oval  shape,  like  the 
horizontal  half  of  an  egg,  being  ten  feet  long,  seven  feet  broad,  and 
three  feet  deep:  the  deck,  a  perfect  oval,  is  convex,  Avith  a  man-hole 
and  cover  in  the  centre.  A  kelson  of  pine  timber,  eighteen  inches 
deep  and  fourteen  inches  broad,  is  fitted  to  the  inside,  running  fore 
and  aft,  and  fayed  on  to  the  shape  of  the  bottom  upon  the  rivets; 
and  the  mooring-bolt,  with  a  broad  bearing-shoulder,  is  passed 
diagonally  up  through  this  kelson  and  firmly  secured  by  a  large  nut 
over  a  plate  of  iron  or  washer  on  the  top  of  the  same.  This  mooring- 
bolt  is  also  fixed  at  one -third  the  length  of  the  hull  from  the  large 
end  or  breast,  and  along  the  other  two-thirds  of  the  bottom  an  iron 
keel,  fifteen  inches  deep  and  250  pounds  Aveight,  is  rivetted  on  Avith 
angle  iron,  and  bolted  through  the  kelson,  Avhich  keeps  the  buoy 
steady  to  the  tide,  and  also  gives  it  stability.  To  the  side  or  rim, 
which  is  eighteen  inches  deep  and  inclined  imvards,  uniting  the 
deck  with  the  bottom,  eight  triangular-shaped  Avooden  uprights  are 
fixed  at  equal  distances  in  outside  sockets  bolted  through  with  nuts 
and  screAvs:  these  stancheons  are  nine  feet  in  length,  terminating  and 
dovetailing  into  an  oval  platform,  five  feet  by  four  feet,  and  are 
braced  horizontally  by  two  rows  of  corresponding  pieces  at  equal 
distances  from  each  other,  the  first  roAv  being  four  feet  from  the 
deck;  and  the  divisions  above  this  are  nearly  filled  up  by  the  vertical 
battens  to  the  top  of  the  platform,  all  firmly  united  Avith  hoop  iron. 
There  are  also  tAvo  diagonal  braces  of  rod-iron,  which  cross  each 
other  in  the  centre  of  the  structure;  Avhilst  seats  are  fixed  at  each 
end  on  a  level  with  the  first  horizontal  brace  pieces,  affording  accom- 
modation for  six  persons,  and  leaving  standing  room  for  six  more  in 
the  centre  of  the  deck.  Under  the  platform  a  large  bell  is  fixed, 
Avith  four  swinging  clappers  hanging  round  it  from  the  platform  and 
striking  the  outside;  Avhilst  the  centre  clapper  has  its  stem  below  the 
hammer  elongated  Avith  rod -iron  to  five  feet,  terminating  in  a  wind- 


112 

cross  of  thin  sheet  iron,  so  as  to  ring  the  bell  with  the  least  breeze 
when  the  water  is  too  smooth  to  affect  the  clappers. 

Above  the  platform,  arching  from  side  to  side,  is  a  semi-circle  of 
square  iron  rod,  which  assists  in  uniting  the  sides  or  top  ends  of  the 
uprights  or  stancheons  to  the  platform,  and  to  which  rim  is  rivettcd 
a  plate  of  thin  iron,  with  the  name  of  the  buoy  painted  on  it;  and 
above  the  centre  of  this  arch,  forming  the  apex  of  the  buoy-beacon, 
is  a  spindle  carrying  a  pyramidal  speculum,  ten  inches  in  angle, 
which,  revolving  freely  as  the  buoy  moves,  reflects  the  rays  of  the 
sun  and  moon,  and  occasionally  Calshot  light.  The  reflected  flashes 
of  the  sun's  rays  are  visible  at  a  distance  of  seven  to  eight  miles 
from  a  vessel's  deck,  and  the  buoy-beacon  itself  is  seen  in  clear 
weather  four  to  five  miles  off,  or  three  times  the  distance  of  ordinary 
buoys  of  the  largest  size;  in  thick  weather  it  looms  like  a  small  ves- 
sel at  anchor.  The  top  of  the  speculum  is  twelve  feet  above  the 
water-line. 

The  commanders  of  steamers  and  other  vessels  frequenting  the 
port  of  Southampton,  and  all  the  pilots,  give  a  unanimously  favorable 
report  of  this  buoy-beacon,  and  strongly  recommend  its  general 
adoption  upon  all  outstanding  dangers;  they  say  that  it  rises  over 
the  tops  of  the  seas  without  plunging  or  diving,  or  being  in  the  least 
affected  by  the  action  of  the  tide  beyond  sheering  from  side  to  side 
within  the  scope  of  its  mooring  chain  during  a  gale  across  the  tide, 
and  thus  rendering  itself  more  conspicuous  by  presenting  two-thirds 
of  its  broadside  each  way  alternately;  and  in  heavy  gales  of  wind 
yffroni  the  most  exposed  quarters,  namely.  SE.  and  WSW.,  at  the 
strongest  period  of  a  spring  tide,  it  is  seen  to  ride  upon  the  crest  of 
waves  that  completely  overwhelm  the  neighboring  buoys  of  the 
Bramble,  Leep.  &c.  It  has  not  been  baled  or  pumped  out  since  it 
first  went  into  the  water,  and  upon  taking  off  the  manhole-cover, 
after  it  had  been  laid  down  six  months,  it  was  found  to  be  as  tight  as 
a  cup.  As  a  proof  of  its  stability,  two  persons  at  one  time  have  sat 
on  the  top  of  the  platform  when  afloat,  without  its  showing  any  signs 
of  being  crank.  The  cost  of  this  buoy-beacon,  including  bells,  fit- 
tings, <fec.,  was  £55. 


113 


Letter  from  Jacob  Herbert,  csq.,  Secretary  to  the  Trinity  Home  Corpo- 

ration. 


TRINITY  HOUSE,  LONDON, 

September  3,  1851. 

Sm:  I  beg  to  acknowledge  the  receipt  of  your  letter,  dated  27th 
May  last,  stating  that  you  are  directed  by  the  Light-house  Board  in 
session  in  conformity  to  a  recont  act  of  Congress  (copy  of  which  is 
therewith  transmitted)  to  address  this  corporation,  for  the  purpose 
of  obtaining  information  which  it  is  considered  they  may  be  enabled 
to  furnish,  either  of  a  general  or  specific  character,  with  a  view  to 
the  improvement  of  the  present  condition  of  the  lights  and  other  aids 
to  navigation  belonging  to  the  Government  of  the  United  States;  and 
thereupon  calling  the  attention  of  the  Elder  Brethren  to  certain  par- 
ticular inquiries  deemed  of  major  importance,  embracing  a  period 
of  time  subsequent  'to  the  date  of  the  House  of  Commons's  report 
of  1845. 

And  having  laid  the  same,  with  its  accompanying  printed  docu- 
ments, before  the  board,  I  am  instructed  to  communicate  to  you,  as 
secretary  of  the  Light-house  Board  of  America,  the  following  replies 
which  the  Elder  Brethren  have  directed  to  be  given  to  the  queries 
referred  to,  in  the  order  in  which  they  occur  in  your  said  letter,  aud 
which  I  trust  will  convey  the  desired  information. 

I  have  the  honor  to  be,  sir,  your  most  obedient  servant, 

J.  HERBERT. 
To  Lieut.  THORNTON  A.  JENKINS, 

U.  S.  N.,  Washington  City,  U.  S. 


Q.  As  to  the  changes  which  may  have  been  made  in  the  mode  of 
constructing  light-house  towers;  the  different  descriptions  of  mate- 
rials used,  which  is  considered  the  best  under  all  circumstances, 
referring  specially  to  durability,  economy,  and  efficiency  as  perma- 
nent structures,  having  regard  to  annual  expense  for  repairs? 

A.  The  mode  of  construction  remains  unchanged,  except  that,  as 
respects  material,  iron-plate  houses  have  been  erected  in  some  of  the 
British  colonies.     As  a  general  rule,  stone  is  preferable,  but  much 
depends  on  locality  and  other  circumstances. 
8 


114 

Q.  What  has  been  the  experience  of  the  board  in  the  use  of  the 
screw-pile  and  Potts' s  cylinders  for  special  locations  where  hydraulic 
structures  would  have  been  attended  with  great  expense  or  difficul- 
ties which  could  not  have  been  easily  overcome?  What  objection, 
if  any,  to  cast-iron  hollow  towers  in  general?  What  has  been  the 
effect  of  vibration  and  torsion  of  the  pile  structure  and  of  vibration 
upon  the  hollow  cast-iron  towers,  so  far  as  the  Trinity  board  has 
been  informed  ? 

A.  Neither  the  screw-pile  nor  Dr.  Potts' s  cylinder  have  been  ex- 
tensively used  by  the  Trinity  House.  The  vibration  of  the  pile 
structures  is  sensibly  felt.  No  torsion  has  been  observed.  The 
board  has  had  no  experience  of  cast-iron  hollow  towers. 

Q.  The  results  of  trials  of  mortars  and  cements  for  stone  and  brick 
towers  ;  the  effect  of  the  sea  atmosphere  on  hydraulic  and  other 
light-house  structures  ? 

A.   These  are  points  for  the  opinions  of  engineers. 

Q.   Improvements,  if  any,  in  illuminating  apparatus  since  1845? 

A.  The  dioptric  lights  have  been  improved  by  the  substitution  of 
/.ones  of  prisms  for  concave  mirrors. 

Q.  What  number  of  new  lens  or  Frcsriel  lights?  What  number  of 
old  reflector  lights  renewed  by  the  introduction  of  the  lens  apparatus, 
and  what  the  whole  number  of  lights  introduced  since  1845?  Have 
lenses  of  the  smaller  classes  been  introduced  for  harbor  and  river 
purposes? 

A.  Three  new  lens  lights  have  been  established,  viz  :  one  at  Tre- 
vose  Head,  and  two  in  Sea  Reach.  The  Milford  high,  Eddystone 
and  Spurn  low  lights  have  been  renewed  in  the  manner  mentioned  ; 
u  catadioptric  apparatus  of  the  first,  second,  and  fourth  orders,  re- 
spectively, having  been  substituted  for  the  Argand  lamps  and  para- 
bolic reflectors  theretofore  in  use  thereat.  Lenses  of  the  fourth 
order  have  been  introduced  and  still  are  in  use  for  harbor  and  river 
lights. 

Q.  What  the  comparative  useful  effect  and  economy  of  that  class 
or  order  of  lights,  with  the  reflector  lights  in  similar  positions? 
What  the  relative  economy  and  useful  effect  of  the  two  systems  as 
demonstrated  by  experiment  at  the  South  Foreland  lights  and  other 
places  in  a  series  of  years,  all  things  else  being  equal? 

A.  The  comparative  economy  depends  upon  the  number  of  lamps 
required  under  the  old  or  reflective  system. 


115 

Q.  What  lamp  is  in  most  general  use  in  the  lens  lights,  the  Carcel, 
pneumatic,  or  hydraulic  lamp  ?  The  advantages  arising  from  the  use 
of  the  one  or  the  other  ? 

A.  The  hydraulic  or  fountain  lamp  is  universally  in  use  in  the 
light-houses  of  the  corporation,  with  one  exception  (the  South  Fore- 
land high)  where  the  light  is  shown  from  a  Carcel  lamp  ;  the  disad- 
vantage arising  from  the  use  of  which  is  the  occasional  derangement 
of  the  machinery. 

Q.  What  the  most  approved  lamp  for  reflector  lights  ? 

A.  An  Argand  lamp  :  the  burner  seven-eighths  of  an  inch  in 
diameter. 

Q.  What  improvements  in  ventilation?  Have  Prof.  Faraday's 
tubes  been  generally  introduced  ? 

A.  Prof.  Faraday's  tubes  have  been  fitted  at  all  the  light-houses. 

Q.  How  often  do  the  best  quality  parabolic  reflectors  in  use  in  the 
Trinity  House  lights  require  renewing? 

A.   Not  for  many  years  with  care — say  from  twenty-five  to  thirty. 

Q.  How  long  do  the  best  slide  lamps  and  burners  last  with  ordi- 
nary repair  ? 

A.  The  best  Argand  burners,  when  new,  last  from  two  to  three 
years  ;  the  lamps  a  much  longer  period. 

Q.  What  is  the  difference  in  first  cost  and  what  the  difference  in 
annual  expense  of  the  two  systems,  comparing  lights  of  the  same 
class  or  order  of  the  two  systems  in  which  other  circumstances  are 
equal  ?  What  the  difference  in  useful  effect,  &c.,  &c.? 

A.  The  difference  in  first  cost  is  in  favor  of  the  reflector  lights,  as 
follows,  viz  : 

For  the  dioptric  apparatus  complete,  about £1,030 

Lantern,   pedestal,  &c.,  &c 1,940 

2,970 

Reflecting  apparatus  complete,  about 

Lantern,   pedestal,  &c.,  &c 1,940 

2,328 

Difference £642 

Q.  Have  any  difficulties  attended  the  management  of  the  Carcel, 
or  other  single  burner  lamps,  since  the  introduction  of  the  lens  lights 
into  Great  Britain  ? 


116 

A.  No  difficulties  have  attended  their  management ;  the  only  dis- 
advantage is  pointed  out  under  the  above  reply  to  the  third  query. 

Q.  What  difference  is  made  in  regard  to  numbers,  salaries,  and 
qualifications  of  keepers  in  the  two  systems? 

A.  No  difference  is  made  in  these  respects. 

Q.  Have  any  improvements  been  made  in  the  illuminating  appa- 
ratus of  light-ships?  Are  Argand  burners  and  parabolic  reflectors 
mounted  on  gimballs  used  on  board  the  Trinity  House  light-ships  ? 

A.  Argand  burners  and  parabolic  reflectors  mounted  on  gimballs 
are  used  on  board  the  Trinity  House  light-vessels. 

Q.   What  kind  of  fog-signals  are  employed? 

A.   A  gong  is  sounded. 

Q.  Have  any  new  modes  of  distinguishing  lights  been  introduced  ? 
and  what  are  now  employed  ? 

A.  No  new  modes  have  been  introduced.  Distinctive  character  is 
obtained  by  varieties  of  fixed,  revolving,  intermittent,  and  colored 
lights. 

Q.  What  number  of  persons  constitute  the  crews  and  officers  of 
light- vessels  in  exposed  positions,  and  what  number  in  rivers,  bays, 
<fcc.,  <fec. ;  what  the  tonnage  of  the  light-vessels  on  the  Goodwin 
sands  and  in  other  exposed  situations  ? 

A.  Eleven  persons  in  all,  consisting  of  a  master,  mate,  and  nine 
seamen,  excepting  in  one  instance,  in  which  the  number  of  men  is 
fifteen,  (seventeen  hands  in  all.)  One  hundred  and  sixty  tons,  more 
or  less,  by  builders'  measurement. 

Q.  What  descriptions  of  oils  are  used  in  the  lights  of  England  ? 

A.   Colza  or  rapeseed,  refined. 

Q.  How  are  they  tested  before  being  received  ? 

A.  Tested  by  experimental  burnings. 

Q.  What  number  of  light-vessels  kept  for  relief? 

A.  One  in  each  district ;  the  number  of  floating  light  stations  in 
the  several  districts  varying  from  eleven  to  three. 

Q.  What  has  been  the  result  of  trials  with  colza  or  rapeseed  oil, 
chemical  and  gas  lights,  etherial  oils,  &c.,  &c.?  Do  you  use  different 
qualities  of  oils  for  winter  and  summer  ? 

A.  The  result,  at  present,  is  the  invariable  use  of  refined  oil  from 
rapeseed,  as  before  stated.  No  other  oil  is  used. 

Q.  Of  what  materials  are  lanterns,  in  general,  constructed  for  the 
Trinity  House  lights  ? 

A.  Lanterns  are  constructed  of  copper  or  gun  metal. 


117 

Q.  What  advantages  arise  from  the  use  of  bronze  ? 

A.  Bronze,  like  gun  metal,  does  not  corrode. 

Q.  What  description  and  sizes  of  glass  for  seacoast  lights  ? 

A.  Plate  glass  :  the  dimensions  of  the  panes  vary.  In  the  first 
order  lights  from  48  by  41  inches  to  35  by  29;  second  order  lights 
from  41  by  39  inches  to  22  by  19.  The  thickness  of  the  glass  being 
ordinarily  three-eights  of  an  inch;  in  exposed  situations  five-eighths 
of  an  inch. 

Q.  How  is  the  glass  put  in,  by  being  glazed  with  putty,  or  by 
other  means  ? 

A.  The  panes  are  fixed  by  means  of  a  composition  of  white  and  red 
lead  termed  plate-glass  cement. 

Q.  What  precautions  are  observed  to  repair  such  casualties  as  the 
breaking  of  glass  by  wild  fowl,  mechanical  lamps,  or  movable  ma- 
chinery getting  out  of  order,  &c.  ? 

A.  No  precaution  is  taken  against  the  breaking  of  the  glass  by 
wild  fowl,  but  spare  panes  are  kept  in  store  ;  instances  of  breakage 
are  very  rare.  Movable  machinery,  &c.,  seldom  gets  out  of  order, 
and  no  particular  precaution  is  therefore  considered  necessary. 

Q.  What  precautions  are  taken  to  prevent  unnecessary  waste  of 
light  by  absorption  in  the  lanterns  ? 

A.   The  inner  part  of  the  lanterns  is  painted  white. 

Q.  Are  seacoast  or  other  first  class  lights  permitted  to  be  left  after 
lighting  up  at  sun-setting  and  before  being  extinguished  at  sun-rising, 
without  a  keeper  in  the  lantern  ? 

A.  No.  A  keeper  is  always  in  the  watch-room.  (Vide  printed  in- 
structions to  light-keepers.) 

Q.  What  is  the  general  system  of  inspection  ?  How  often,  and  by 
what  class  of  persons  ? 

A.  By  superintendents  of  districts,  and  frequently  by  members  of 
the  board. 

Q.  How  are  supplies  delivered — by  tenders,  or  by  contract  vessels? 
How  often  per  annum,  and  under  whose  direction,  &c.  ? 

A.  By  the  corporation's  vessels  once  a  year  ;  or  oftener,  if  neces- 
sary, under  the  board's  order. 

Q.  What  the  comparative  expense  of  the  Maplin  sand  screw-pile 
light,  with  a  first  class  light-ship,  per  annum,  and  which  is  the  most 
efficient  ? 


118 

A.  The  Maplin  screw-pile  light  in  the  year  1849  cost,  say  £455. 
The  light- vessel  at  the  north  end  of  the  Goodwin  sand,  say  £1,048. 

Q.  Any  information  on  the  subject  of  buoys,  beacons,  and  sea- 
marks, with  reference  to  inspection,  distinction,  &c.,  is  desired. 

A.  They  are  constantly  inspected,  and  are  distinguished  by  differ- 
ence of  color  and  character. 

Q.  Modes  of  giving  publicity  to  proposed  changes  in  regard  to 
lights,  <fec.  How  long  before  the  change  is  made,  and  what  specific 
means  employed  to  give  extended  circulation  at  home  and  abroad  ? 

A.  By  advertisement  in  the  principal  daily  newspapers  of  the  me- 
tropolis, <fec.,  in  a  few  of  the  periodicals  generally  perused  by  mari- 
ners. Separate  notices  are  also  fixed  up  and  distributed  at  the  dif- 
ferent custom-houses,  and  copies  sent  to  the  consuls-general  of  the 
various  foreign  governments  likely  to  be  interested  in  the  notifica- 
tions. In  some  cases  preliminary  notices  are  issued. 

Q.  Any  printed  forms,  circulars,  reports,  descriptive  lists,  general 
and  special  instructions.  <fcc..  upon  the  subject  of  lights,  buoys,  and 
beacons,  under  the  Trinity  House  corporation,  will  be  most  accept- 
able. 

A.  General  instructions  to  light-keepers ;  general  instructions  to 
masters  and  mates  of  light-vessels  :  directions  for  the  management  of 
refracting  and  reflecting  lights  to  light-keepers  ;  directions  for  the 
management  of  reflecting  lights  on  board  light- vessels ;  various  forms 
of  account  of  oil,  &c.;  inventory  of  stores  for  a  light- vessel. 


Extracts  from  the  report  of  the  Hon.  R.  J.  Walker,  Secretary  of  the 
Treasury,  August  5,  1846.  (Senate  document,  No.  488,  1st  session, 
29th  Congress.) 

[Report  of  Lieutenants  T.  A.  Jenkins  and  R.  Bacbe,  United  States  Navy.] 

"  In  countries  where  the  system  of  lighting  is  good,  a  general  plan 
for  the  classification  of  lights,  selection  of  sites,  construction  of  the 
light-houses  and  apparatus,  and  inspection,  has  been  adopted,  or  im- 
provements have  been  slowly  introduced  under  the  direction  of  ex- 
isting authorities.  The  most  perfect  system  in  Europe  is  the  result, 
of  the  former  plan;  and  it  must  be  obvious,  that,  for  a  growing  coun- 
try like  ours,  no  other  can  secure,  on  the  greater  part  of  the  coast,  a 
due  attention  to  the  wants  of  commerce  and  navigation. 


119 

"The  unequal  distribution  of  lights  upon  different  important  parts  of 
our  coast  proves  this,  and  shows  how  desirable  it  is  that  some  general 
plan  should  be  fallen  upon,  by  which  the  claims  of  different  parts  of 
the  country  might  be  duly  considered,  a  light  provided  wherever  it  is 
desirable  to  navigation,  and  expenditure  saved  when  no  such  necessity 
exists;  that,  when  a  light-house  was  decided  to  be  necessary,  the  site 
of  the  buildings  should  be  properly  selected,  the  buildings  properly 
constructed  so  as  to  combine  stability  and  economy;  all  the  acces- 
sories, as  store -houses  for  oil  and  for  lighting  apparatus,  for  fuel, 
and  the  like,  properly  arranged;  that  the  lighting  apparatus  should 
be  of  the  most  approved  kind  and  construction,  and  so  placed  as  to 
illuminate  the  required  part  of  the  horizon  without  waste;  that  the 
lights  should  be  properly  classified,  so  that,  from  the  large  seacoast 
light  to  the  small  harbor  light,  the  buildings,  lighting  apparatus,  and 
accessories  might  be  on  the  proper  scale:  the  distinctive  character 
for  the  lights  adopted  which  experience  has  shown  most  effective,  as 
fixed,  revolving,  fixed  lights  with  flashes,  successions  of  bright  light 
and  eclipses  at  regular  intervals,  and  lights  of  particular  colors:  that 
when  ready  for  illumination,  the  lighting  apparatus  may  be  properly 
kept  and  attended  to,  under  effective  inspection. 

"  It  is  not  possible  to  leave  such  things  as  these  to  local  information, 
derived  at  second  hand,  or  to  chance,  without  paying  dearly  in  the 
end  for  the  want  of  system. 

"In  all  these  points  it  appears  that  other  countries  have  advanced 
rapidly;  and  it  becomes  us  to  see  what  improvements  introduced  else- 
where are  adapted  to  our  use,  and  to  ascertain  how  our  general  sys. 
tern  may  be  modified. 

"A  comparison  of  the  lighting  apparatus  in  use  with  us,  and  of  the 
improved  apparatus  of  France,  shows  that  in  this  essential  our  pro- 
gress has  not  been  as  great  as  might  have  been  desired. 

"The  reports  of  the  inspecting  officers  detailed  from  the  navy  to  ex- 
amine the  lights  on  our  coast  showed  their  absolute  defects;  the 
present  report  shows  their  deficiencies  relative  to  those  of  other 
countries.  The  trial  made  of  one  of  the  French  lights,  at  the  en- 
trance to  New  York  harbor,  at  Sandy  Hook,  has  been  very  success- 
ful, but  the  use  of  this  apparatus  has  not  been  extended.  A  light- 
house need  be  seen  from  particular  parts  of  the  horizon  only;  and  as 
the  lamps  used  throw  off  their  lights  almost  equally  on  all  sides,  the 


120 

direction  of  portion  of  the  rays  must  be  changed.  This  may  be  done 
by  reflection  from  opake  substances,  as  from  metallic  mirrors;  or 
by  bending  or  refracting  by  transparent  bodies,  as  by  glass  prisms 
or  lenses.  Much  more  light  is  lost  by  the  use  of  the  most  highly 
polished  surfaces  as  reflectors,  than  by  passing  through  transparent 
bodies;  and  hence  lenses  are  more  Tiseful  and  economical  for  light- 
house purposes  than  mirrors.  The  refracting  or  lens  apparatus  in- 
vented in  France  by  Augustin  Frcsnel,  has  been  generally  applied 
under  the  direction  of  his  brother,  Leonor  Fresnel,  the  present  ac- 
complished secretary  of  the  Board  of  Light-houses. 

"In  this  apparatus,  lenses  of  glass  are  used  to  throw  the  light  of 
powerful  lamps  in  the  required  directions  upon  the  horizon,  and  the 
partAvhich  would  otherwise  escape  upwards  is  reflected  to  the  horizon 
by  glass  prisms,  so  placed  that  the  rays  fall  upon  the  back  or  second 
surfaces  of  the  prisms,  at  angles  at  which  they  are  entirely  reflected. 
The  lenses  are  built  up  of  separate  pieces  of  glass,  thereby  saving 
the  weight  and  cost  of  large  masses  of  material,  besides  diminishing 
the  thickness,  and  thus  preventing  the  loss  of  light  by  absorption, 
and  permitting  the  figure  of  the  surface  to  be  adjusted  so  as  to  bring 
the  rays  accurately  to  a  focus.  If  the  lens  apparatus  be  made  to 
revolve,  the  navigator  will  see  brilliant  flashes  of  light,  gradually 
growing  dim,  and  succeeded  by  short  intervals  of  comparative  dark- 
ness; and  if  a  second  set  of  lenses,  suitably  arranged,  revolve  about 
the  first,  which  remains  fixed,  a  general  illumination  will  be  varied 
by  brilliant  flashes;  these  maybe  white  or  colored;  and  thus  the 
appearance  of  lights  may  be  so  varied  as  to  make  them  distinctive. 
A  single  large  lamp,  supplied  with  oil  by  mechanism,  (as  in  French 
light-houses,)  or  by  hydrostatic  pressure,  (as  in  some  of  the  English 
ones,)  is  used  with  the  lens  system,  and  produces  great  economy  in 
the  consumption  of  oil  necessary  to  supply  a  given  quantity  of  light. 

"The  dimensions  of  the  apparatus  are  easily  varied  to  suit  the  differ- 
ent quantities  of  light  required,  from  the  small  harbor  light  to  the 
large  seacoast  light.  In  the  French  system,  the  lights  are  divided 
into  four  orders,  the  first  being  the  most  powerful;  and  erch  order 
may  be  sub-divided  into  a  larger  or  smaller  size.  The  best  reflecting 
lights  do  not  more  than  reach,  in  power,  the  second  order  of  the  lens 
system. 

'•The  advantages  of  the  Fresnel  or  lens  system  are :  1st,  in  the  greater 
brilliancy  of  light;  2d,  in  the  greater  quantity  of  the  more  brilliant 


121 

light  thrown  upon  the  horizon;  and  3d,  in  the  less  consumption  of 
oil  in  obtaining  these  advantages.  Simple  experiments  and  calcula- 
tions based  upon  them  give  an  unerring  means  of  ascertaining  the 
relative  brilliancy,  quantity,  and  economy  of  different  lights.  If  two 
lights  are  equally  bright,  they  will  illuminate  equally  two  equal  sur- 
faces placed  at  the  same  distance  from  them.  If  one  is  brighter  than 
the  other,  the  brighter  will  illuminate  equally  the  same  surface  when 
farther  from  the  light;  a  fourfold  brightness  corresponding  to  a  dou- 
ble distance,  a  ninefold  brightness  to  a  triple  distance,  and  so  on. 
Thus  it  is  easy  to  compare  the  relative  brightness  of  lamps,  and 
adopting  the  light  of  some  particular  lamp  as  the  standard,  to  describe 
other  lights  as  equivalent  in  brightness  to  once,  twice,  or  more  times 
the  standard. 

"The  useful  effect  of  a  light  depends  not  only  on  its  brightness,  but 
on  the  extent  of  horizon  which  it  can  illuminate.  The  average  bril- 
liancy in  different  directions,  multiplied  by  the  extent  of  horizon  over 
which  it  shines,  gives  its  useful  effect.  Its  economy  is  measured  by 
this  useful  effect  directly  and  inversely  by  the  consumption  of  oil 
required  to  obtain  it. 

"The  careful  experiments  of  Mr.  Fresnel  leave  no  doubt  of  the  great 
advantages  in  respect  to  brilliancy,  useful  effect,  and  economy  of  the 
lens  system,  as  may  be  seen  by  a  few  examples. 

'  'A  harbor  light  on  the  lens  system,  of  the  smaller  size  of  the  fourth 
order,  with  a  single  mechanical  lamp  burning  l^th  ounce  avoirdu- 
pois of  oil  per  hour,  would  give  twice  as  brilliant  a  light  as  the  ordi- 
nary reflecting  system  having  a  lamp  burning  1£  ounce  avoirdupois 
of  oil  per  hour.  The  quantity  of  light  on  the  horizon  would  be  dou- 
ble, the  cost  of  a  given  quantity  of  light  one-half,  and  therefore  the 
economy  two-fold.  As  the  apparatus  increases  in  size  from  this  to 
the  higher  orders,  the  advantage  of  the  lens  system  increases.  In 
the  third  order,  second  size,  a  mechanical  lamp  with  a  double  wick, 
burning  6£  ounces  avoirdupois  of  oil  per  hour,  gives  as  much  light  as 
fourteen  lamps  with  reflectors,  each  burning  1£  ounce  avoirdupois  of 
oil  per  hour.  The  useful  effect  is  one  and  a  half  times,  and  the 
economy  between  three  and  four  fold.  In  the  second  order  of  lights 
the  new  system  for  equal  useful  effects  is  three  times  as  economical 
as  the  old,  reaching  in  the  larger  sizes  to  four-fold.  A  power  equiva- 


122 

lent  to  that  of  the  first  order  of  lens  lights  has  not  been  reached  by 
the  reflecting  system. 

"The  cost  of  the  erection  of  buildings  for  the  new  system  of  light- 
ing, and  the  first  cost  of  the  apparatus  itself  is  somewhat  more  con- 
siderable, and  the  number  of  keepers  required  is  greater  than  with 
the  old;  the  repairs,  on  the  contrary,  are  much  less.  An  accurate 
comparison  of  these  particulars  shows  that  in  France  the  economy  is 
in  favor  of  the  new  system.  Thus,  taking  into  consideration  the 
interest  on  the  cost  of  tower,  lantern,  reflectors  or  lenses,  and  of 
keeping  up  the  light,  the  relative  expense  of  the  two  plans  for  a 
small  harbor  light  is  as  236  to  the  new  to  226  of  the  old  plan;  while 
the  quantity  of  light  on  the  horizon  is  as  2  to  1  in  favor  of  the  new; 
and  hence  the  economical  effect  is  nearly  double  upon  the  new  sys- 
tem. For  a  large  revolving  light  (second  order)  the  annual  outlay 
for  the  old  and  new  systems  would  be  a?  126  to  208,  while  the  useful 
effect  would  be  only  as  1  to  2,  and  the  economical  effect  of  the  new 
system  would  be  more  than  one  and  a  half  that  of  the  old.  The  cost 
for  the  lens  apparatus  might  for  the  present  be  greater  in  our  own 
country:  but  the  economy  in  lighting  by  the  lens  system  is  too  great 
for  this  circumstance  to  turn  the  balance  against  it. 

"The  mechanical  lamp  used  with  these  lights,  or  some  other  which 
American  ingenuity  may  supply,  or  the  hydrostatic  or  pneumatic 
lamp  in  use  in  the  English  light-houses,  will  replace  with  advantage 
the  present  imperfect  lamp.  In  France,  the  mechanical  lamp  is  found 
to  require  but  small  repairs,  readily  made  in  establishments  where 
the  lamps  are  constructed;  and  both  construction  and  repairs  would 
surely  be  practicable  here.  The  cost  of  repairs  of  the  lens  appa- 
ratus is  in  a  series  of  years  merely  nominal,  and  experience  has  shown 
that  it  is  more  secure  and  more  easily  seen  than  the  old.  No  impor- 
tant seacoast  lights  should  be  left  without  being  watched  by  a  keeper, 
and,  in  the  economy  in  lighting,  will  much  more  than  pay  the  cost  of 
two  keepers  in  the  larger  light-houses. 

"Whether  the  rapeseed  oil  generally  used  in  the  French  light- 
houses may  be  employed  in  our  own  with  advantage,  is  a  question 
which  cannot  now  be  settled;  it  may,  however,  be  desirable  to  call 
the  attention  of  farmers  to  the  cultivation  of  the  plant  from  which 
it  is  obtained. 

"The  use  of  the  screw-pile,  for  the  foundation  of  light-houses,  has, 
by  rendering  the  establishment  of  permanent  structures  upon  banks 
and  shoals  comparatively  easy,  safe,  and  economical,  superseded  in 


123 

many  cases  the  use  of  light-boats,  which,  especially  in  exposed  posi- 
tions, are  of  comparatively  little  value. 

'  The  buoys  used  in  the  entrances  to  our  harbors  are  now  placed  by 
local  authorities,  and  under  loose  regulations.  A  general  system 
should  be  adopted  of  coloring  and  numbering,  and  should  be  so 
rigidly  adhered  to  that  the  seaman  would  know  his  position  as  soon 
as  he  discovered  a  buoy.  This  is  practicable,  as  will  be  seen  from 
the  interesting  account,  in  the  report  of  Lieutenants  Jenkins  and 
Bache,  of  the  intricate  approaches  to  the  port  of  Liverpool,  which 
are  rendered  quite  safe  by  the  system  of  buoys,  lights,  marks,  and 
tide  signals.  The  natural  marks  which  disappear  yearly  from  our 
coast  should  be  replaced  by  permanent  ones;  screw-piles  for  mooring 
buoys  should  in  certain  cases  be  supplied.  The  arrangements  for 
placing  buoys  and  verifying  their  positions  require  to  be  rendered 
systematic,  and  to  be  subjected  to  some  general  control.  The  navi- 
gator should  have  due  notice  of  all  changes  from  a  source  connected 
with  the  whole  light-house  system. 

"The  best  modes  of  lighting  would  be  ineffective  unless  the  keepers 
were  careful  and  intelligent  persons,  and  instructed  in  the  necessary 
particulars  of  the  business.  Some  training  is  desirable.  Frequent 
reports,  and  perhaps  the  suggestion  in  regard  to  keeping  meteoro- 
logical and  tide  registers,  as  a  means  of  securing  attention  and  intel- 
ligence, may  be  adopted." 


Extracts  from  Senate  Document  No.  488,  1st  session,  29th  Congress. 

[Repoit  of  Lieuts.  T.  A.  Jenkins  and  E.  Bache,  U.  S.  N.,  to  the  Secretary  of  the  Trcasmy, 
August  5,  1846  ] 

LIVERPOOL   BAY   AND   HARBOR. 

The  buoys  are  constructed  of  both  wood  and  iron.  Those  of  iron 
are  being  pretty  generally  introduced  by  the  surveyor.  Six  of  the 
largest  employed  are  of  that  material,  and  he  expresses  a  decided 
preference  for  them,  both  in  ah  economical  point  of  view  and  as  a 
matter  of  expedienc}r.  They  are  constructed  with  water-tight  com- 
partments, so  that  there  is  no  danger  of  their  filling  should  they  be 
injured  by  a  vessel  coming  in  contact  with  them.  Galvanized  iron, 
both  for  buoys  and  for  the  hoops  of  wood  ones,  is  highly  approved 
of.  The  expense  is  the  great  obstacle.  For  buoys  to  be  painted 


124 

white,  there  can  be  little  doubt  of  the  great  advantage  of  using  the 
galvanized  iron  for  hoops.  Can  and  nun  buoys  are  employed.  (See 
accompanying  drawings.)  The  iron  buoys  require  a  weight  to  each 
to  make  them  float  properly  in  the  water,  but,  once  properly  ballast- 
ed, there  is  no  further  difficulty  with  them  in  that  respect.  The 
buoys  are  of  good  sizes,  fine  proportions,  and  are  distinguished  by 
their  color,  shape,  number  and  name/"  Here,  as  in  all  the  ports  of 
the  kingdom,  red  buoys  are  placed  on  the  starboard  hand  of  the 
channels  leading  from  seaward,  and  the  black  ones  on  the  port  hand. 
The  numbers  commence  from  seaward.  At  the  end  of  spits,  or  at 
turning  points,  perches  are  placed  on  the  buoys  (of  iron.)  So  well 
and  perfectly  are  the  buoys  distinguished  that  a  man,  to  go  wrong, 
must  be  unable  to  read,  or  to  distinguish  colors. 

The  moorings  of  the  buoys  are  heavy  iron  sinkers,  so  moulded  as 
to  increase  their  tenacity  of  hold,  with  the  heavy  chains  sent  from 
the  light-vessels  as  unfit  for  use,  although  perfectly  good  and  appli- 
cable to  this  purpose. 

There  are  in  the  store  duplicates  of  all  the  buoys;  they  are  painted 
regularly  once  in  six  months,  and  their  moorings  raised  every  year. 

The  buoys  and  light-vessels  are  placed  in  their  proper  positions 
by  the  surveyor  himself,  the  positions  being  fixed  and  decided  upon 
by  angles,  so  that  the  exact  spots  are  known  upon  which  to  place 
them,  and  from  which  they  are  never  allowed  to  be  removed,  unless 
alteration  of  shoals  or  channels  make  it  necessary,  (when  it  becomes 
necessary  to  consult  the  Trinity  corporation,  London,)  or  by  accidents 
occurring  to  them;  in  which  latter  case  a  few  hours  only  are  allowed 
to  elapse  before  they  are  replaced. 

Registers  of  the  buoys  are  kept,  (see  form,)  showing  when  they 
were  made,  when  repaired,  and  when  placed,  &c.,  with  a  column 
showing  their  positions  by  angles,  remarks,  &c.  The  present  cour- 
teous and  intelligent  marine  surveyor  of  the  port  of  Liverpool,  (Lieu- 
tenant Lord,  R.  N.,)  is  greatly  in  favor  of  iron  as  a  material,  as  well 

o  Thus :  "  Red  buoys  on  the  starboard  hand,  and  black  on  the  larboard,  when  running  in." 

"  Black  and  white  striped  buoys  on  intervening  banks  or  flats." 

Superior  can  buoys,  with  perches  at  the  "elbows  or  turning  points  of  principal  channels." 

"Each  buoy  bears  the  initial  of  the  channel  it  occupies,  thus:  F.  Farmby  channel.  C. 
Crosby  channel.  HF.  Ilalf-lide  SicatcJ.way;  N.  New  channel.  H.  Horse  channel.  R.  Rock 
channel.  HE.  Helbrt  swash.  B.  Beggars'  Patch.  L.  Hoylake.  V .  Victoria  channel." 

'The  buoys  are  likewise  numbered  in  rotation,  No.  1  denoting  the  outer  or  seaward  buoy 
of  the  channel  its  letter  indicates. ' ' 


125 

for  light- vessels  as  for  buoys.  The  Northwest  light-ship  is  203  tons, 
and  cost  no  more  than  one  of  the  same  size  of  wood  would  have  cost, 
while  the  advantages  in  many  respects  are  greatly  on  the  side  of  the 
iron.  The  larger  the  vessel  the  greater  the  economy  of  iron  in  com- 
parison to  wood.  They  draw  but  little  water,  (the  Northwest  only  nine 
feet,)  and  are  fitted  with  bilge  keels  to  keep  them  from  rolling  too 
heavily.  The  greatest  possible  attention  is  paid  to  all  moorings. 
Experiments  have  been  made  upon  chains  of  different  sizes,  &c. 
Those  in  use  at  present  are  fitted  with  wrought-iron  studs,  and  have 
been  found  to  answer  infinitely  better  than  those  with  cast  iron  ones; 
the  former  seldom  or  never  falling  out. 

This  corporation,  not  satisfied  apparently  with  this  perfect  system 
of  lighting,  &c.,  has  further  provided  for  the  safety  of  seamen  by 
adding  a  number  of  life-boats  to  their  charge.  We  are  aware  that 
this  does  not  come  strictly  within  the  limits  of  our  instructions;  but 
finding  it  intimately  connected  with  the  light-house  establishment, 
and  having  heard  of  the  many  and  great  benefits  which  have  resulted 
from  it  as  being  a  part  of  the  most  complete  whole,  we  deem  it  but 
proper  to  refer  to  it  in  this  connexion. 

The  boats  (nine  in  number)  are  placed  at  different  stations  around 
the  bay,  well  provided  and  well  protected  from  the  weather,  ready 
at  a  moment's  notice  for  service.  The  crews  are  composed  of  expe- 
rienced watermen  residing  near  the  stations  of  the  boats,  always 
willing  and  anxious  to  render  assistance  to  those  who  may  be  so  un- 
fortunate as  to  strike  upon  the  shoals,  or  meet  with  any  other  acci- 
dent within  the  vicinity  of  the  bay  and  harbor. 

To  insure  a  more  certain  and  prompt  assistance  to  those  in  distress, 
the  corporation  has  an  arrangement  with  the  Steam-tug  Company,  by 
which,  for  the  consideration  of  400  guineas  per  annum,  and  25 
guineas  additional  for  every  time  a  steamer  is  required,  a  vessel  is 
ready  at  all  times,  day  and  night,  with  steam  up,  for  towing  out  a 
life-boat,  and  for  rendering  any  service  that  may  be  required. 

A  simple  inspection  of  the  chart  of  the  bay  of  Liverpool  will  suffice 
to  explain  the  manner  of  masking  the  lights,  by  which  the  positions 
of  the  buoys  are  pointed  out  by  night  to  the  pilot,  so  that  he  can 
stand  on  his  course  with  confidence.  The  system  is  simple  and  per- 
fect, meriting  the  warmest  eulogies  of  all  persons  feeling  any  interest 
in  the  commerce  of  the  port. 


126 


LIGHT-HOUSES   OF   SCOTLAND. 

The  '•  Commissioners  of  Northern  Lights,"  who  are  charged  with 
the  control  and  management  of  light-houses,  buoys,  beacons,  <fcc.,  of 
a  general  character,  on  the  coasts  of  Scotland,  were  first  instituted 
by  act  of  Parliament  in  1786. 

The  board  is  composed  of  twenty -five  commissioners  or  members, 
whose  services  are  gratis,  and  whose  professions  are  of  a  civil  charac- 
ter, but  chiefly  that  of  the  law.  There  is  not  a  single  nautical  person 
attached  to  the  board. 

There  is  a  secretary  to  the  board  and,  an  engineer  who  is  the  ex- 
ecutive officer  ;  an  auditor,  and  an  accountant,  who  prepares  all  ac- 
counts for  the  committees,  &c. 

The  local  or  harbor  lights,  fifty-one  in  number,  arc  under  the  con- 
trol and  management  of  local  authorities  and  trustees,  supported  by 
dues  levied  upon  the  shipping  visiting  the  respective  ports  where  the 
lights  are  established. 

The  general  board  meets  four  times  a  year  for  the  transaction  of 
business.  It  receives  and  acts  upon  the  proceedings  of  the  commit- 
tee meetings  which  have  been  held  in  the  interim. 

There  is  a  standing  committee,  composed  of  sixteen  members,  call- 
ed the  "Bell  Rock  committee,'''  which  meets  once  a  fortnight  during 
the  year,  except  in  the  months  of  April,  August  and  September.  This 
committee  has  charge  of  the  lights,  and  appoints  the  finance  commit- 
tee, before  which  the  auditor  is  required  to  lay  all  accounts  twice  a 
year,  when  they  are  examined  and  passed. 

There  is  also  a  committee  regulating  "superannuated  allowances," 
and  one  for  "buoys,  beacons,"  &c. 

Committees  are  appointed  for  the  superintendence  of  light-houses 
in  the  course  of  erection  ;  and  the  board  is  in  the  habit  of  remitting 
any  matters  of  importance  which  may  arise  to  the  consideration  of  a 
special  committee,  which  examines  and  reports  upon  them. 

The  engineer  of  the  board  attends  upon  all  the  committees.  He 
executes  all  orders  relating  to  lights,  buoys,  beacons,  &c.,  and  has 
the  entire  management  of  the  executive  department.  He  receives  a 
salary  of  £700,  and  an  allowance  of  £200  additional  for  clerk  hire. 

There  are  no  agents  for  the  inspection  of  lights.  The  engineer 
goes  around  to  all  the  stations  at  least  once  a  year,  and  reports  the 


127 

result  of  his  observations  to  the  board.  There  are  two  persons  in  the 
engineer's  department:  the  "superintendent  of  light-keepers'  du- 
ties," who  is  charged  with  the  delivery  of  stores  at  each  station,  ac- 
companying the  tender  which  delivers  them,  (which  takes  place  gene- 
rally twice  a  year,)  reporting,  on  leaving  the  station,  the  condition 
in  which  ho  found  the  establishment ;  and,  on  his  return,  is  required 
to  hand  over  to  the  engineer  the  diary  of  his  journey,  in  which  is  en- 
tered the  observations  made  by  him  upon  each  station.  The  other 
person  is  the  "foreman  of  light-house  repairs,"  who,  assisted  by  one 
or  two  men,  goes,  as  occasions  may  require,  to  repair  the  lamps  and 
light-house  apparatus  in  general. 

The  engineer  makes  out  a  requisition  once  a  year,  according  to  a 
printed  form,  (hereto  annexed,)  for  all  stores  that  may  be  required 
for  each  light-house.  These  requisitions  are  submitted  to  a  sub-com- 
mittee, which  rejects  such  items  as  may  not  be  satisfactorily  explain- 
ed by  the  engineer,  and  approves  all  those  deemed  necessary  for  the 
service. 

Printed  forms  are  then  issued  to  different  parties,  generally  in  Ed- 
inburgh, one  of  which  each  party  retains,  and  returns  the  other,  with 
the  prices  attached  to  each  item  required,  accompanied  by  patterns 
or  samples.  The  lowest  tenders  are  always  taken  in  the  cases  of  or- 
dinary supplies.  Tnere  are  no  public  newspaper  advertisements  for 
supplies  ;  but  applications  are  made  to  parties  who  are  considered 
able  to  undertake  the  contract. 

The  supplies  are  delivered  at  the  storehouse  at  Leith,  compared 
by  the  engineer,  the  superintendent  of  light-keepers'  duties,  and  the 
foreman  of  repairs,  and,  if  found  to  correspond"  with  the  requirements 
of  the  tender,  are  received  in  store,  from  whence  they  are  forwarded, 
in  the  tenders  belonging  to  the  establishment,  to  the  different  stations, 
as  before  mentioned.  There  are  at  present  two  light-house  tenders, 
and  it  is  proposed  lo  build  another,  to  be  propelled  by  steam. 

All  applications  for  new  lights,  <fec.,  are  submitted  to  the  standing 
committee.  Examinations  are  made  for  proper  sight?,  &c.  ;  and,  if 
deemed  necessary,  after  having  obtained  the  approbation  of  the  Trini- 
ty Corporation  of  England,  proceed  with  the  work.  The  engineer 
presents  the  plans,  specifications,  &c.,  which  must  be  approved  by 
the  board  before  the  commencement  of  the  work.  The  light-houses 
are  generally  built  by  contract,  under  the  immediate  direction  and 
superintendence  of  the  engineer  of  the  board,  and  a  superintendent 


128 

who  is  not  permitted  to  leave  the  spot,  after  the  commencement  of 
the  work,  until  it  is  completed  and  received  by  the  board.  All  extra- 
ordinary repairs  are  made  in  the  same  manner. 

The  buildings  are  constructed  chiefly  of  the  dark  stone  or  granite 
peculiar  to  the  coasts,  in  a  plain,  substantial  manner.  The  oil  cellars 
are  fitted  and  finished  with  a  proper  care,  as  in  England  and  France  : 
the  keepers'  houses  are  separate  from  the  towers,  and  differ  very  lit- 
tle in  their  general  arrangements  from  those  of  England.  One  very 
simple  and  useful  custom  of  calling  the  keepers  from  their  dwellings 
to  the  towers,  a  distance  ordinarily  of  forty  or  fifty  feet,  was  observ- 
ed, which  removes  all  necessity  for  the  keeper  to  leave  the  light-room 
until  regularly  relieved.  This  consists  of  a  small  metal  air-tube,  lead- 
ing from  the  lantern  to  the  room  of  the  keeper,  at  the  end  of  which 
are  bells,  which  are  struck  by  small  hammers  of  wood,  raised  by 
blowing  into  the  tube.  The  keeper,  upon  being  called,  answers  in 
the  same  manner  ;  the  one  making  the  call  reversing  the  hammer  of 
his  bell  after  making  the  signal,  so  that  the  answer  may  be  made. 

The  light-keepers'  houses  are  furnished  with  spare  rooms  for  the 
engineer,  and  for  the  workmen  who  visit  the  stations  for  making  any 
repairs  that  may  be  required  upon  the  illuminating  apparatus.  The 
furniture  of  these  rooms  is  supplied  by  the  commissioners. 

The  domes  of  the  lanterns  are  all  double-roofed  of  copper.  No 
lightning  rods  are  used. 

The  reflectors  are  parabolic,  and  generally  twenty-one  inches  in 
diameter  for  the  fixed  lights,  and  twemty-four  inches  in  diameter  for 
the  revolving  lights. 

The  lights  are  distinguished  very  much  as  they  are  under  the 
Trinity  board,  with  some  little  modification.  In  a  few  cases  there 
are  two  lights,  placed  one  above  the  other,  in  the  same  tower — a  plan 
not  to  be  approved  of  under  ordinary  circumstances.  The  number 
of  burners  varies  from  one  to  forty-eight  for  each  station,  or  from 
one  to  twenty-seven  for  each  light-house;  the  average  for  each  light 
being  about  twenty. 

The  lamps  employed  in  the  dioptric  lights  are  the  same  as  those 
employed  in  France.  Those  employed  in  the  reflector  lights  are 
Argand  fountain  lamps,  with  burners  containing  wicks  of  about  one 
inch  in  diameter.  Great  care  is  bestowed  upon  the  manufacture  of 
these  lamps,  which  have  their  burners  tipped  with  silver,  to  prevent 


129 

their  too  rapid  destruction  by  the  great  heat  of  the  flame  produced 
by  them. 

The  Argand  lamps  are  solidly  made  of  brass,  and  of  different  forms; 
although  those  most  modern,  most  approved  of,  and  most  in  use,  are 
fitted  with  a  slide  apparatus  accurately  formed,  by  which  the  burner 
may  be  removed  from  the  interior  of  the  reflector  at  the  time  of 
cleaning  or  wiping  it,  as  also  for  trimming  the  lamp,  and  returned  to 
exactly  the  same  place,  and  locked  by  means  of  a  key.  The  arrangement 
is  an  admirable  one,  as  it  insures  the  burner  always  being  in  the  focus, 
and  does  not  require  that  the  reflector  be  lifted  out  of  its  place  every 
time  it  is  cleaned.  The  reflectors  are  securely  screwed  to  the  frame, 
and  the  focal  points  marked  upon  them  for  the  flames  of  the  lamps. 
The  lamps  are  made  in  Edinburgh,  and  the  reflectors  in  Birmingham, 
as  a  general  rule.  Lamps  are  also  made  in  Birmingham.  Great  at- 
tention has  been  paid  to  the  ventilation  of  the  Scotch  light-houses. 
Professor  Faraday's  tubes  are  highly  approved  of,  although  they  in- 
crease the  consumption  of  oil. 

The  engineer  to  the  Board  of  "Northern  Lights"  has  the  entire  man- 
agement of  the  lights  in  the  executive  department.  He  selects  his 
assistants  to  act  under  him  in  the  construction  of  buildings,  and  visits 
the  lights  at  least  once  a  year.  They  are  also  visited  by  the  super- 
intendent of  the  light-keeper's  duties,  and  by  the  foreman  of  the 
light-house  repairs. 

The  light-keepers  are  appointed  by  the  board.  Should  they  fail 
in  their  duty,  the  engineer  reports  them  to  the  board.  There  are 
two  keepers  at  each  light-house — one  a  principal,  with  a  salary  of 
<£50  per  annum,  and  an  assistant,  with  a  salary  of  <£40  per  annum. 
At  the  Bell  Rock  and  Skerryvore  there  are  one  principal,  one  prin- 
cipal assistant,  and  two  assistants;  with  salaries,  for  the  keepers,  of 
about  £70,  principal  assistant  <£65,  and  the  assistants  each  £60.  In 
addition  to  their  salaries,  they  are  allowed  each  a  suit  of  uniform 
clothing  or  watch  cloak  once  in  three  years.  They  are  also  allowed  a 
piece  of  ground  large  enough  to  produce  grass  for  a  cow,  and  a  small 
garden.  New  keepers  are  instructed  in  their  duties  for  three  months. 

In  addition  to  the  returns  required  of  the  keepers  of  their  expendi- 
tures of  oil  and  other  supplies,  they  are  required  to  keep  a  baromet- 
rical and  thermometrical  journal,  with  remarks  upon  the  winds  and 
weather. 


130 

They  are  suppled  with  timekeepers,  and  their  dwellings  are  kept 
well  painted  and  repaired;  they  were  in  good  order. 

There  are  no  light-vessels  on  the  coast  of  Scotland. 

The  beacons  and  buoys  are  under  the  immediate  direction  of  the 
"committee;"  under  the  direction  of  which  they  are  placed,  in- 
spected, repaired,  &c.  The  buoys  are  made  of  wood,  and  examined 
and  painted  twice  a  year. 

"Since  the  rule  for  exhibiting  the  lights  between  'sunset  and  sun- 
rise' has  been  adopted  in  Scotland,  an  increased  expenditure  of  oil 
has  been  occasioned.  This  increase,  if  we  estimate  four  hundred  and 
ninety-two  burners  Sut  five  gallons  more  throughout  the  year,  which 
seems  a  fair  allowance,  is  two  thousand  six  hundred  and  forty  gallons. 
or  about  XT8G  13s.  9c?.  per  annum.  The  former  rule,  of  making  the 
'going  away  and  return  of  daylight'  as  the  times  of  lighting  and 
extinguishing,  was  departed  from  with  a  view  to  uniformity  of 
practice." 


FRENCH   LIGHTS. 

The  light-house  department  of  France  is  attached  to  the  official 
duties  of  the  minister,  Secretary  of  State  for  the  Interior,  and  is 
under  the  immediate  control  and  direction  of  the  Minister  of  Public 
Works,  charged  with  the  administration  of  the  bridges  and  roads. 

A  central  public  board  has  the  management  of  all  light-houses, 
buoys,  beacons,  and  sea-marks  on  the  coasts,  which  is  composed  of 
eleven  distinguished  scientific  and  professional  individuals,  who  are 
appointed  by  the  government,  including  the  engineer,  secretary  to 
the  commission,  and  his  assistant.  This  board  is  presided  over  by 
the  Minister  of  Public  Works,  and  in  his  absence  by  the  Under  Secre- 
tary of  State  for  that  department. 

This  mixed  commission,  called  the  "Commission  des  Phares," 
is  composed  of  naval  officers,  (of  whom  there  is  a  majority,)  of 
inspectors  of  the  corps  of  bridges  and  roads,  and  of  members  of  the 
Institute.  It  prepares  the  projets  for  all  new  lights,  and  the  general 
council  of  bridges  and  roads  judges  of  the  propriety  of  all  schemes 
for  that  branch  of  service,  under  the  four  heads  of  architectural 
design,  mode  of  executing  the  works,  estimate  of  the  expense,  and 
the  preparation  of  the  specifications  of  the  works.  The  light-house 
commission  of  France  is  not  an  administrative  body,  but  is  occupied 


131 

solely  in  questions  of  principle  or  design,  and  leaves  to  the  general 
directory  of  bridges  and  roads  the  care  of  providing  the  necessary 
means  for  the  construction  of  new  works,  the  expenses  of  illumi- 
nation, &c. 

The  central  commission  at  Paris  is  charged  with  the  duty  of  pro- 
viding all  supplies  necessary  for  keeping  the  illuminating  apparatus 
in  perfect  order.  There  is  also  in  Paris,  belonging  to  this  particular 
branch  of  the  public  service,  a  central  workshop  and  depot,  under 
the  immediate  care  and  supervision  of  the  secretary-engineer  to  the 
commission,  who  superintends  the  construction  (by  mechanics  em- 
ployed by  the  administration)  of  all  lanterns  and  their  fixtures  that 
may  be  required  for  the  service;  tests  all  apparatus  before  sending  it 
to  its  destination;  makes  experiments  upon  all  the  optical  and  mechani- 
cal portions  of  apparatus  destined  for  light-house  purposes,  combus- 
tibles, &c. ;  in  short,  this  officer  is  charged  with  all  the  scientific 
details  of  the  service,  subject  to  the  instructions,  from  time  to  time, 
which  may  be  issued  by  the  light-house  commission.  At  this  central 
depot  are  always  kept,  ready  for  immediate  use,  the  various  articles 
required  in  the  illuminating  department,  such,  for  example,  as  me- 
chanical und  Argand  lamps,  glass  chimneys,  wicks,  cleaning  materials, 
<fcc. ;  also  specimens  of  the  different  descriptions  of  apparatus  used 
in  light-houses,  and  apparatus  constructed  upon  the  latest  and  most 
approved  plans  ready  for  service. 

All  expenses  incurred  in  the  maintenance  of  the  lights  and  their 
appendages  are  defrayed  by  the  agents  of  the  national  treasury,  from 
funds  authorized  by  annual  appropriations  for  those  specific  purposes. 

No  light  dues  are  charged  upon  shipping  in  France  as  in  Great 
Britain,  Holland,  Denmark,  Norway,  and  Sweden,  <fec. ;  but  the  whole 
establishment  is  provided  for  as  in  the  United  States  and  Eussia. 

The  maintenance  of  the  light-house  buildings  is  confided  to  the 
departmental  or  local  engineers,  and  the  expenses  are  defrayed  from 
funds  appropriated  for  the  service  of  the  department  of  public  works. 

The  establishment  of  new  works  is  decided  upon  by  the  Minister  of 
Public  Works,  under  the  advice  of  the  light-house  commission.  The 
determination  of  the  minister  is  reported  officially  by  the  secretary 
of  the  commission  to  the  Under  Secretary  of  State  for  that  depart- 
ment, and  through  his  office  to  the  prefect  of  the  department  in 
which  the  proposed  work  is  to  be  established.  The  prefect  directs 
the  chief  engineer  of  bridges  and  roads  for  that  department  to  have 
detailed  plans  and  estimates  prepared  upon  the  basis  of  the  proposi- 


132 

tion  of  the  light-house  commission;  these  plans  and  estimates  are 
transmitted  through  the  office  of  the  Under  Secretary  of  State  to  the 
secretary  of  the  light-house  commission,  who  makes  a  report  to 
accompany  them  to  the  light-house  commission.  The  plans  and  esti- 
mates are  then  submitted  to  the  light-house  commission,  which  decides 
whether  or  not  the  wants  of  the  service,  nauticatty  or  othenviss,  are 
such  as  to  require  the  construction  of  the  proposed  works.  In  the 
preparation  of  these  plans  and  estimates  the  military  engineer  of  the 
department  is  consulted,  to  ascertain  his  opinions  as  to  the  propriety 
of  constructing  these  works  with  reference  to  the  defences  of  the 
coast. 

The  details  having  been  completed,  after  having  undergone  the 
strictest  scrutiny  in  every  particular,  the  projet  is  presented  to  the 
general  council  of  bridges  and  roads,  to  be  considered  with  reference 
to  the  architectural  designs,  mode  of  construction,  estimates  of 
expense,  &c.  Having  been  approved  by  the  general  council  of 
bridges  and  roads  and  the  Minister  of  the  Interior,  the  plan  is  then 
sent  to  the  prefect  of  the  department  in  which  the  light  is  to  be 
established,  with  instructions  to  enter  into  contracts  for  the  execution 
of  the  works,  under  the  specifications  and  limitations  authorized  by 
the  administration. 

The  execution  of  these  works  is  entrusted  to  the  engineers  of 
bridges  and  roads  for  that  department.  As  the  works  advance,  the 
contractor  receives  payments  upon  the  certificates  of  the  engineers 
in  charge,  approved  by  the  prefect  of  the  department,  from  the 
departmental  paymaster,  (as  deputy  of  the  public  treasury,)  and  the 
sums  are  charged  to  the  budget  for  works  of  navigation,  under  the 
head  of  light-houses. 

The  light-house  towers  of  France  are  constructed  in  the  most  sub- 
stantial and  perfect  manner  possible,  without  there  being  any  appear- 
ance of  unnecessary  or  wasteful  expenditure.  Great  care  is  taken  in 
the  interior  arrangements  of  the  buildings,  so  that  they  may  best 
answer  the  requirements  of  the  service.  Many  of  the  towers  are 
constructed  of  a  soft  stone  of  a  rather  peculiar  kind,  which  hardens 
by  exposure  to  the  action  of  the  atmosphere;  those  constructed  of 
that  material  are  lined  inside  with  brick,  leaving  a  sufficient  space 
between  the  interior  of  the  outer  wall  and  the  brick  to  allow  a 
free  circulation  of  air,  thereby  securing  the  building  from  dampness. 
Hard  burnt  bricks  are  preferred  for  light-house  towers,  when  circum- 
stances will  admit  of  their  being  employed,  particularly  in  fitting  up 


133 

the  oil  apartments,  which  are  placed  below  the  surface  of  the  earth, 
to  insure  as  equable  a  temperature  during  the  whole  year  as  may  be 
possible  to  attain.  The  keeper's  apartments  are  finished  and  fitted 
up  in  a  plain,  substantial,  and  economical  manner,  combining  all 
the  necessary  accommodation  and  comfort.  There  is  a  room  fitted 
up  and  properly  furnished  for  the  accommodation  of  the  engineer, 
inspector,  or  other  person  authorized  to  make  official  visits,  at  each 
light  station.  Especial  care  is  taken  to  secure  proper  ventilation  to 
the  towers  and  lanterns — all  the  necessary  fixtures  about  the  light- 
rooms,  lanterns,  apparatus,  &c. — the  most  minute,  and  apparently 
unimportant  details  in  the  exterior  and  interior  arrangements;  in 
short,  nothing  could  combine  greater  perfection  in  stability,  in  use- 
fulness, and  a  proper  economy,  than  is  perceptible  in  everything 
connected  with  the  light-houses  visited  by  us  on  the  coasts  of 
France. 

The  repairs  of  the  light-houses  and  their  appendages  are  projected 
and  executed  by  the  engineers  of  the  different  departments  in  which 
they  exist,  who  are  limited  as  much  as  possible  in  their  expenditures 
by  the  estimates  of  each  year  for  those  specific  purposes.  In  some 
cases  the  contractor-general  is  authorized  to  make  repairs,  under  the 
direction  of  the  agents  of  the  administration  of  bridges  and  roads. 

"Whenever  application  is  made  for  a  new  harbor  light,  the  subject 
is  submitted  to  a  local  commission,  assisted  by  the  engineers  of  the 
department.  The  report  is  discussed  by  the  light-house  commission, 
and  the  same  course  subsequently  followed  as  in  the  case  of  large  or 
seacoat  lights. 

All  the  light-house  towers  in  France  are  furnished  with  lightning 
conductors,  made  of  copper  wire  twisted  into  the  form  of  a  rope, 
and  about  three -fourths  of  an  inch  in  diameter. 

In  the  organization  of  the  lighting  service,  two  systems  are  fol- 
lowed— the  contract  and  the  administrative.  The  ocean  and  Medi- 
terranean coasts  are  under  contract  at  present  for  nine  years  from 
1839,  for  all  the  detail  supplies  of  the  service. 

Among  the  clauses  and  conditions,  it  will  be  perceived  that  the  con- 
tractor-general is  required  to  be  represented  by  a  deputy  in  each 
department  in  which  there  are  any  lights;  that  the  oil  of  colza,  clari- 
fied and  refined,  must  be  used  exclusively;  and  that  the  prices  of  oil 
will  be  regulated  quarterly,  based  upon  the  average  prices  of  the 
principal  market  in  the  kingdom  for  that  particular  article  of  com- 
merce. M.  Fresnel  insists  that  this  last  clause  has  had  a  most  salu- 


134 

tary  effect  of  insuring  the  best  oil  the  market  could  produce,  without 
the  contractor  running  any  risk  of  loss.  On  the  coast  of  the  channel, 
from  the  frontier  of  Belgium  to  St.  Halo,  this  service  is  performed 
by  the  administration,  except  for  the  article  of  oil,  which  is  procured 
under  a  contract  entered  into  for  three  years.  That  portion  of  the 
coasts  of  France  which  is  lighted  by  contract  includes  even  the  sala- 
ries of  the  light-keepers;  but  where  the  service  is  performed  by  the 
administration,  the  keepers  are  appointed  by  the  prefect  of  the 
department,  upon  the  recommendation  of  the  engineers.  The  smaller 
articles  necessary  to  the  illumination  are  sent  from  the  central  depot 
in  Paris,  under  the  charge  of  a  conducting  steward.  The  mechani- 
cal lamps  are  sent  to  Paris  to  be  repaired  under  the  engineer-secre- 
tary to  the  light-house  commission.  The  administrative  system 
recommends  itself,  for  the  reason  that  it  avoids  all  intervention  of 
interest  foreign  to  that  for  which  the  lights  were  established.  The 
contract  system  has  been  for  a  long  time  preferred  in  France,  for 
reasons  of  economy,  complication  of  accounts  when  performed  by  the 
administration,  &c.;  but  the  experience  of  the  last  seven  years  on 
the  channel  coast  has  sufficiently  demonstrated  the  importance  of 
changing  it  to  the  administrative;  and  it  is  deemed  quite  probable 
that,  after  the  expiration  of  the  present  leases,  that  system  will  be 
exclusively  adopted,  except  for  supplies  of  oil. 

The  superintendence  of  the  lights  of  France  is  confided  to  the 
local  engineers  of  the  corps  of  bridges  and  roads.  The  secretary  to 
the  light-house  commission  visits,  each  year,  one  of  the  three  divi- 
sions into  which  the  coast  is  divided,  and  his  assistant  another,  so 
that  the  inspections,  as  far  as  possible,  are  biennial  for  each  division. 
Monthly  returns  are  made  of  all  stores  on  hand,  of  the  quantity  of 
oil  consumed  each  night.  &c.,  to  the  secretary  of  the  commission. 
These  returns  are  intended  as  checks  upon  the  keepers  and  answer 
the  purpose  admirably.  A  most  rigid  supervision  is  required  at  the 
hands  of  the  inspecting  engineers;  and  moreover,  that  they  employ 
all  possible  means  to  detect  any  delinquency  on  the  part  of  the  keep- 
ers, or  other  agents  connected  with  the  service.  It  is  conceded  that 
all  these  precautions  may  fail  to  produce  the  desired  effect,  but  that 
under  such  a  supervision  few  among  the  guilty  will  escape  detection. 
The  lights  visited  by  the  undersigned  were  clean,  and  presented 
every  indication  of  a  perfect  and  systematic  attendance  and  super- 
vision. 


135 

Indications  of  the  range  of  visibility  afford  very  meagre  data  for 
forming  a  correct  idea  as  to  the  relative  value  of  apparatus  for  illu- 
mination. It  is  impossible  to  determine  with  certainty  the  absolute 
range  of  any  light,  in  consequence  of  the  different  conditions  of  the 
atmosphere,  and  of  the  capacities  of  different  observers.  A  first  or- 
der dioptric  light  has  been  seen^fo/  miles  very  often,  and  one  of  the 
fourth  order  as  far  as  sixteen  miles.  M.  Fresnel  says,  upon  the  sub- 
ject of  range :  "  We  would,  then,  draw  very  erroneous  conclusions  as 
to  the  relative  value  of  the  useful  effect  of  the  apparatus  of  these 
lights,  in  taking  for  a  basis  of  comparison  the  indications  of  range, 
which  are  never  fixed,  or  positive." 

At  the  present  time  there  are  two  systems  of  illumination  in 
France — the  old  or  reflector  system,  and  the  new  or  dioptric  system. 
In  1822,  M.  A.  Fresnel  placed  the  first  dioptric  apparatus  ever  suc- 
cessfully employed,  in  the  tower  of  Cordouan,  at  the  mouth  of  the 
Gironde.  In  1825,  the  light-house  commission  decided  upon  the 
exclusive  use  of  the  lenticular  apparatus  for  the  illuminations  of  the 
coasts  of  France  and  colonies;  adopting,  at  the  same  time,  the  pro- 
gramme and  report  of  Rear  Admiral  de  Rossel,  who  had  been 
charged,  as  a  member  of  the  "Commission  des  Phares,"  with  that 
service. 

Since  that  period  new  lights  have  been  established,  and  old  ones 
replaced  with  this  new  apparatus,  until,  on  the  31st  December,  1845, 
there  were,  of  the  two  hundred  and  nine  lights  of  every  description 
belonging  to  the  light-house  department  of  France,  one  hundred  and 
nineteen  fitted  with  that  apparatus.  The  remaining  ninety  lights 
were  reflector  lights,  fitted  with  the  Bordier  Marcet  (called  "side- 
ral")  reflectors,  and  the  parabolic  reflectors,  similar  to  those  used  in 
Great  Britain  and  America.  Of  these  last  ninety  lights,  seventy- 
seven  are  small  harbor  or  temporary  lights,  fitted,  in  most  cases, 
with  a  single  parabolic  or  Bordier  Marcet  reflector,  marking  the 
entrance  to  some  channel  or  harbor.  The  remaining  thirteen  are 
fitted  with  lenticular  apparatus  of  the  most  approved  construction, 
in  accordance  with  the  original  plan  of  1825. 

Engineers  and  other  scientific  and  philanthropic  individuals,  of 
most  if  not  of  all  the  nations  of  the  world,  have  made  this  new  sys- 
tem of  illumination  an  object  of  study  and  of  critical  examination ; 
the  results  of  which  have  been  the  successful  though  gradual  appli- 
cation of  it  to  the  coasts  of  nearly  all  the  commercial  nations. 
|  On  the  31st  December,  1845,  eighty-three  light-houses  belonging  to 


136 

foreign  governments  had  been  fitted  with  lenticular  apparatus  con- 
structed in  Paris,  to  which  may  be  added  those  constructed  in  Eng- 
land and  Holland,  say  from  fifteen  to  twenty,  making,  including  those 
on  the  coasts  of  France,  upwards  of  two  hundred  and  ten;  one  hundred 
of  which  may  be  put  down  as  of  the  three  first  orders,  and  the  remain- 
ing one  hundred  and  ten  of  the  fourth  order.  These  numbers  do  not 
include  those  at  present  in  the  course  of  construction  for  France, 
Egypt,  (tower  at  Alexandria,)  Brazil,  and  the  colonies,  islands  in  the 
Pacific,  &c.  M.  Fresnel  says,  with  perfect  truth  and  reason:  "After 
these  numerous  and  extended  applications,  the  dioptric  system  of 
lights  may  be  fully  appreciated  under  the  double  aspect  of  theory  and 
practice;  and  I  will  add,  that  under  the  first  point  of  view  the  ques- 
tion has  been  for  a  long  time  out  of  controversy." 

There  are  six  different  orders  of  lenticular  apparatus  at  present 
employed,  viz:  first,  second,  third  larger  model,  third  smaller  model, 
fourth  larger  model,  and  fourth  smaller  model. 

The  different  orders  are  subjected  to  different  combinations,  such 
as  dioptric,  two  catadioptric — one  with  concave  mirrors,  and  the 
other  with  catadioptric  zones,  or  rings  of  glass,  in  triangular  profile 
sections — and  the  "diacatopric,"*  combining  the  dioptric  portion 
and  the  catadioptric  zones  surmounted  by  plane  mirrors.  In  ad- 
dition, a  spherically  curved  metallic  reflector  or  mirror  is  placed  on 
the  land  side  of  all  lights  which  are  only  required  to  illuminate  from 
four-fifths  to  five-sixths  of  the  horizon,  which  reflects  the  rays  from 
that  side  back  through  the  opposite  lenses. 

"There  can  be  no  doubt,'7  says  a  distinguished  engineer, t  who 
has  had  much  to  do  with  the  light-houses  of  Europe,  "that  the  more 
fully  the  system  of  Fresnel  is  understood  the  more  certainly  will  it 
take  the  place  of  all  other  systems  of  illumination  for  light-houses,  at 
least  in  those  countries  where  this  important  branch  of  administra- 
tion is  conducted  with  the  care  and  solicitude  which  it  deserves." 
"To  the  Dutch  belongs  the  honor  of  having  first  employed  the  sys- 
tem of  Fresnel  in  their  lights."  "The  commissioners  of  northern 
lights  followed  in  the  train  of  improvements,  and  in  1834  sent  Mr. 
Alan  Stevenson  on  a  mission  to  Paris,  with  full  powers  to  take  such 
steps  for  acquiring  a  perfect  knowledge  of  the  dioptric  system,  and 
for  forming  an  opinion  of  its  merits  as  he  should  find  necessary." 

*  See  Mr.  Alan  Stevenson's  report  to  commissioners  of  northern  lights,  for  this  word, 
f  Mr.  Alan  Stevenson,  civil  engineer. 


137 

"  The  singular  liberality  with  which  he  was  received  by  M.  Leonor 
Fresnel,  brother  to  the  late  illustrious  inventor  of  the  system,  and 
his  successor  as  secretary  to  the  light-house  commission  of  France, 
afforded  Mr.  A.  Stevenson  the  means  of  acquiring  such  information 
and  making  such  a  report,  on  his  return,  as  to  induce  the  commis- 
sioners of  northern  lights  to  authorize  him  to  remove  the  reflecting 
apparatus  of  the  revolving  light  at  Inchkeith,  and  substitute  dioptric 
instruments  in  its  place."  *  *  *  "The  Trinity  House  followed 
next  in  adopting  the  improved  system."  *  *  *  "Other  coun- 
tries begin  to  show  symptoms  of  interest  in  this  important  change; 
and  America,  it  is  believed,  is  likely  soon  to  adopt  active  measures 
for  the  improvement  of  their  light-houses.  "Fresnel,  who  is  already 
classed  with  the  greatest  of  those  inventive  minds  which  extend  the 
boundaries  of  human  knowledge,  will  thus,  at  the  same  time,  receive 
a  place  amongst  those  benefactors  of  the  species  who  have  conse- 
crated their  genius  to  the  common  good  of  mankind;  and  wherever 
maritime  intercourse  prevails,  the  solid  advantages  which  his  labors 
have  procured  will  be  felt  and  acknowledged." 

The  fourth  order  lenticular  lights  are  illuminated  ordinarily  by 
means  of  a  common  fountain,  or  constant  level  lamp  and  Argand 
burner,  with  a  single  cylindrical  wick  of  three-fourths  to  seven- 
eighths  of  an  inch  in  diameter,  consuming  about  one  and  a  quarter 
ounce  of  oil  per  hour,  and  forty-eight  gallons  per  annum.  The 
larger  lights  require  mechanical  lamps  with  multiple  wicks,  to  as 
great  a  number  as  four,  placed  in  concentric  tubes,  and  the  oil  sup- 
plied to  them  by  means  of  pumps,  put  in  play  by  clock  machinery. 
Hydraulic  and  pneumatic  lamps  have  been  employed  in  the  place  of 
the  mechanical  ones,  but,  with  good  reason,  they  are  not  approved  of 
in  France.  For  the  catadioptric  apparatus  of  half  a  metre  in  diameter, 
the  ordinary  constant  level  lamps,  with  two  concentric  wicks,  burn- 
ing about  four  and  a  half  ounces  of  oil  per  hour,  have  been  employed 
very  successfully  at  several  points  on  the  coast  of  France,  where  the 
ordinary  range  of  a  light  of  the  third  order,  for  example,  was  not  re- 
quired, or  for  harbor  lights  requiring  a  powerful  ray,  or  one  whose 
brilliancy  it  is  necessary  to  weaken  by  the  application  of  a  red  chim- 
ney, with  the  view  to  give  it  a  distinctive  character.  These  double 
wick  ordinary  lamps  require  only  one  keeper  to  attend  to  them. 
Some  of  the  burners  in  France  are  fitted  with  flat  wicks  for  small 
and  temporary  lights,  although  by  no  means  common,  and  generally 
disapproved  of. 


138 

The  dioptric  lights  of  France  are  divided  into  six  different  orders  ; 
but,  with  reference  to  their  distinctive  characteristics  and  appear- 
ances, this  division  does  not  apply,  inasmuch  as,  in  every  order  or 
class,  lights  of  precisely  the  same  character  may  be  found,  differing 
only  in  the  distance  at  which  they  can  be  seen,  and  in  the  expense 
of  their  maintenance.  The  six  different  orders,  as  before  mentioned, 
are  not  intended  as  distinctions,  "but  are  characteristic  of  the  power 
and  range  of  lights,  which  render  them  suitable  for  different  locali- 
ties on  the  coasts,  according  to  the  distance  at  which  they  can  be 
seen."  "  This  division,  therefore,  is  analagous  to  that  which  sepa- 
rates the  lights  of  Great  Britain  into  sea  lights,  secondary  lights,  and 
harbor  lights — terms  which  are  used  to  designate  the  power  and 
position,  and  not  the  appearance  of  the  lights  to  which  they  are 
applied." 

In  France  there  are  nine  principal  combinations  of  lights  possess- 
ing distinctive  characteristics.  These  distinctions,  for  the  most  part, 
depend  upon  the  periods  of  revolution  rather  than  upon  the  charac- 
teristic appearance  of  the  light.  They  are — 

1.  Flashes,  which  succeed  each  other  every  minute  ; 

2.  Flashes,  which  succeed  each  other  every  half  minute  ; 

3.  Flashes,  alternately  red  and  white  ; 

4.  Fixed  lights,  varied  by  flashes  every  four  minutes  ; 

5.  Fixed  lights,  varied  by  flashes  every  three  minutes  ; 

6.  Fixed  lights,  varied  by  flashes  every  two  minutes  ; 

7.  Fixed  white  lights,  varied  by  red  flashes  more  or  less  frequent; 

8.  Fixed  lights  ; 

9.  Double  fixed  lights. 

There  are  very  few  double  fixed  lights  in  France.  They  are,  how- 
ever, sometimes  employed  for  the  purpose  of  giving  a  very  decided 
character  to  the  locality.  For  example,  the  first  order  lights  at  La 
Heve,  near  the  port  of  Havre,  and  the  two  lights  at  present  in  the 
course  of  construction  on  the  left  bank  of  the  Cancke.  Red  fixed 
lights  are  not  employed  on  the  coasts  of  France,  except  as  a  distin- 
guishing characteristic  for  harbor  purposes.  They  are  doubly  objec- 
tionable :  first,  because  of  the  great  diminution  of  light  in  conse- 
quence of  the  absorption  of  the  red  glass  chimney;  and,  secondly,  it 
loses  its  distinctive  character  in  foggy  weather — all  lights  assuming 
a  reddish  tint  under  those  circumstances. 

The  revolving  reflector  lights  are  objected  to  because  of  the  fact 
that,  ordinarily,  they  are  only  distinguishable  by  the  duration  of 


139 

their  eclipses,  which  often  become  positive  at  a  very  short  distance 
from  the  light-house,  and  the  interval  of  time  between  any  two 
eclipses  could  not  be  extended  to  a  greater  limit  than  three  minutes 
without  prolonging  the  duration  of  the  eclipses  to  such  an  extent  of 
time  as  to  mislead  the  navigator  by  depriving  him  for  so  long  a  time 
of  his  point  of  recognition.  In  the  revolving  dioptric  apparatus, 
upon  the  latest  and  most  approved  plan,  the  duration  of  the  eclipses 
is  scarcely  perceptible  ;  the  fixed  subsidiary  parts  of  which  reflect  a 
light  constantly  visible  in  a  horizon  extending  nine  or  ten  nautical 
miles  with  a  second  order,  and  from  twelve  to  fifteen  with  a  first 
order  apparatus. 

The  three  first  of  the  principal  combinations  only  are  applied  to 
the  first  three  orders,  in  consideration  that  in  the  inferior  orders  the 
flashes  would  have  too  short  a  duration,  and  the  eclipses  would  be 
positive  at  too  short  a  distance  from  the  light,  in  consequence  of  the 
feebleness  of  the  ray  produced  by  the  fixed  subsidiary  part  of  the 
apparatus. 

The  distinguished  engineer,  secretary  to  the  "  Commission  des 
Phares,"  of  France,  M.  Leonor  Fresnel,  kindly  furnished  the  under- 
signed with  the  results  of  numerous  photometric  experiments  which 
were  made  for  the  purpose  of  testing  the  comparative  useful  and 
economical  effects  of  the  two  systems  of  illumination,  to  which  they 
beg  leave  to  call  particular  attention. 

M.  Fresnel  says,  in  his  note  referred  to,  ' '  the  foregoing  results 
confirm  the  following  principles  : 

1.  "The  useful  effect  of  a  parabolic  reflector  increases  with  its 
dimensions  and  with  that  of  the  illuminating  body. 

2.  "The  economical  effect  of   a  reflector  of  given  dimensions  is 
greatest  when  the  lamp-burner  is  smallest. 

3.  "The  divergence  is  greatest  when  the  flame  is  most  voluminous, 
or  when  the  reflector  is  smallest.    We  cannot,  then,  (all  other  things 
being   equal)  augment  the  economical  effect  of  a  reflector  without 
diminishing  its  useful  effect— that  is  to  say,  without  reducing  its 
brilliancy  or  intensity,  and  consequently  its  range  (port6e.) 

' '  The  reduction  of  the  volume  of  light  within  certain  limits  is  par- 
ticularly objectionable  when  it  appertains  to  eclipse  apparatus,  in 
which  case  it  limits  the  width  of  the  luminous  cone,  and  consequently 
augments  the  length  of  the  eclipses.  The  same  reduction  applied  to 
the  foci  of  reflectors  composing  a  fixed  light  apparatus  may  weaken 
the  light  in  their  intervals  to  such  a  degree  as  to  produce  dead  angles, 


140 

or  become  completely  obscured  to  the  observer  beyond  certain  dis- 
tances. 

"It  is  further  proper  to  remark  that  the  horizontal  divergence  is 
not  lost  for  useful  effect,  but  that  the  divergence,  in  the  vertical 
sense,  only  profits  the  navigator  in  the  limited  angular  space  com- 
prised between  the  tangent  at  the  surface  of  the  sea  and  the  ray 
terminating  at  the  distance  of  some  miles  from  the  light. 

"Finally,  there  is  for  the  calibre  of  the  lamp-burners  applicable 
to  reflectors  of  given  dimensions,  and  destined  for  the  illumination  of 
an  equally  determined  range,  a  maximum  beyond  which  prodigality 
of  light  ensues,  and  a  minimum  within  which  the  illumination  be- 
comes insufficient." 

The  third  order  smaller  size  lenticular  apparatus  may  be  illumi- 
nated with  very  decided  advantages  by  means  of  an  ordinary  Argand 
burner  and  single  wick.  Such  a  light  would  consume  about  two 
ounces  of  oil  per  hour,  and  is  admirably  adapted  for  harbor  lights. 
In  ordinary  weather  such  a  light  may  be  seen  from  twelve  to  fifteen 
miles.  One  keeper  alone  can  attend  to  all  the  duties  of  such  a  light, 
and  it  is  maintained  in  France  at  an  annual  expense  of  about  two 
hundred  dollars. 

M.  Fresnel  remarks,  with  reference  to  the  ranges  of  different 
lights,  their  useful  effect,  &c. : 

"The  useful  effect  of  a  light-house  apparatus  is  measured  by  the 
quantity  of  light  which  it  projects  upon  the  horizon.  Observations 
of  range  for  that  purpose  furnish  very  uncertain  evidences,  on  ac- 
count of  the  difficulty  of  ascertaining  the  absolute  range  of  a  light, 
which  varies  according  to  the  state  of  the  atmosphere  and  according 
to  the  good  or  bad  sight  of  the  observers." 

Reflector  lights,  with  not  more  than  six  or  eight  burners,  are 
attended  by  one  keeper,  occasionally  assisted  by  the  members  of  his 
family.  For  lights  with  a  larger  number  of  burners,  two  keepers  ; 
and  if  the  light  be  in  an  isolated  position,  three  keepers  are  allowed, 
with,  in  the  latter  cases,  certain  privileges  not  accorded  to  others. 

Dioptric  lights  of  the  fourth  order  and  third  order  smaller  size, 
require  but  one  keeper,  except  when  in  isolated  positions.  Two 
keepers  are  allowed  to  lights  of  the  third  order  larger  size,  and  for 
those  of  the  second  order,  in  consequence  of  the  employment  of  the 
mechanical  lamp. 

First  order  lights  are  allowed  three  keepers  ;  and  when  there  are 
two  first  order  lights  forming  one  combination,  five  keepers  are 


141 

allowed  for  the  two  lights.  Lights  of  the  first  order  in  isolated 
positions,  are  allowed  four  keepers,  and  for  the  third  order  larger 
size  and  the  second  order  lights,  similarly  situated,  three  keepers 
are  allowed.* 

In  comparing  the  two  systems  of  illumination,  they  should  be  con- 
sidered under  the  heads — first,  of  absolute  useful  and  economical 
effect;  second,  of  first  cost,  repairs,  and  maintenance;  and,  third,  of 
the  facility  and  safety  of  the  service. 

The  brilliancy  of  a  catadioptric  apparatus  of  11.8  inches  interior 
diameter,  lighted  by  a  lamp  burning  forty-five  grammes  of  oil  per 
hour,  has  been  found,  by  photometric  experiments,  to  be  equal  to 
eight  or  nine  Carcel  burners;  while  that  of  a  "sideral"  reflector  of 
Bordier  Marcet,  illuminated  by  a  lamp  consuming  fifty  grammes  of 
oil  per  hour,  has  been  found,  in  the  same  manner,  equal  to  only  four 
burners  of  Carcel ;  or,  in  other  words,  the  brilliancy  of  the  former 
is  to  the  latter  as  one  to  two.  The  useful  effect  of  the  catadioptric 
apparatus,  illuminating  three-fourths  of  the  horizon,  is  represented 
by  137,700,  and  that  of  the  reflector  by  68,400,  which  gives  the 
value  as  one  to  two. 

The  economical  effect  of  the  catadioptric  apparatus  is  represented 
by  3060,  and  that  of  the  reflector  by  1368  ;  giving  the  value  in  that 
respect  as  1  to  2.24. 

No  combination  of  reflectors  can  produce  an  equivalent  to  the  third 
order  smaller  size  apparatus,  illuminated  by  an  ordinary  fountain 
lamp  arid  Argand  burner,  with  one  wick,  consuming  sixty  grammes 
of  oil  per  hour,  or  one  burner,  with  two  wicks,  consuming  one  hun- 
dred and  fifteen  grammes  of  oil  per  hour.  An  apparatus  of  this  sort, 
with  a  lamp  of  two  wicks,  may  be  seen  in  ordinary  weather  (the 
horizon  of  the  light,  from  its  elevation  above  the  sea  level,  being 
equal  to  or  greater  than  that  distance)  at  the  distance  of  fifteen  to 
eighteen  nautical  miles. 

The  brilliancy  of  a  catadioptric  third  order  larger  size  apparatus, 
illuminated  by  a  mechanical  lamp  of  two  wicks,  consuming  one  hun- 
dred and  ninety  grammes  of  oil  per  hour,  (six  and  three-fourth 
ounces)  has  been  found  equal  to  seventy  burners. 

We  suppose  that  it  embraces  only  four-fifths  of  the  horizon.     To 

°  In  England,  Scotland,  and  Ireland,  no  difference  is  made  between  the  number  of 
keepers  for  dioptric  and  reflector  lights. 


142 

illuminate,  by  means  of  reflectors,  the  same  angular  space  of  288°, 
with  an  effect  of  light  about  equal,  fourteen  parabolic  reflectors,  of 
about  eleven  inches  in  diameter,  illuminated  by  Argand  lamps,  con- 
suming each  thirty-five  grammes  of  oil  per  hour,  will  be  required. 
The  useful  effect  of  these  reflectors  will  be  represented  by  870,240, 
and  that  of  the  catadioptric  apparatus  by  1,160,000  ;  and  thus  it  is 
seen,  that  notwithstanding  the  very  great  difference  in  favor  of  the 
catadioptric  apparatus,  in  the  consumption  of  oil,  it  is  also  superior 
in  useful  effect  to  the  light  with  the  fourteen  parabolic  reflectors. 
Further,  the  economical  effect  of  the  catadioptric  apparatus  is  repre- 
sented by  6105,  and  that  of  the  reflector  by  1776,  or  as  1  to  3.44  : 
"that  is  to  say,  without  estimating  the  expenditure  of  oil  by  unity  of 
light,  the  lenticular  light  will  be  nearly  three  and  a  half  times  more 
advantageous  than  the  reflector  light."  With  regard  to  the  effective 
expenditure  of  oil,  they  will  be  in  the  proportion  of  190  grammes  to 
14  X  35  grammes  per  hour,  or  as  1  to  2.6. 

The  brilliancy  of  a  catadioptric  apparatus  of  the  second  order,  with 
a  mechanical  lamp  of  three  concentric  wicks,  consuming  five  hundred 
grammes  of  oil  per  hour,  has  been  found  equal  to  two  hundred  and 
sixty-four  burners.  Supposing  that  it  is  only  required  to  illuminate 
three-fourths  of  the  horizon  ;  then,  to  obtain  an  effect  about  equal  in 
angular  space  of  270°,  at  least  thirty-four  parabolic  reflectors  of  about 
twenty  inches  in  diameter  will  be  required,  which  will  give  a  useful 
effect  which  is  represented  by  3,525,120,  while  that  of  the  catadiop- 
tric apparatus  is  represented  by  4, 120,000.  The  comparison  between 
the  absolute  consumption  of  oil  will  be  equal  to  2.86  to  1  ;  and  that 
of  the  quantity  of  oil  expended  by  unity  of  light  equal  to  3.33  to  1  : 
thus,  under  this  last  report,  the  lenticular  apparatus  will  be  three 
and  a  third  times  as  advantageous  as  the  catoptric  apparatus. 

The  maximum  brilliancy  of  a  revolving  light  of  the  second  order, 
with  twelve  lenses,  has  been  found  to  be  equal  to  1184  burners,  and 
its  minimum  brilliancy  equal  to  one  hundred  and  four  burners.  To 
construct  a  light,  with  parabolic  reflectors,  possessing  an  equal  effect, 
it  will  require  twenty-four  with  diameters  from  twenty-two  inches  to 
twenty-four  inches,  arranged  on  six  faces  of  the  revolving  frame.  In 
making  the  comparison,  however,  for  want  of  precise  data  as  to  the 
lustres  of  those  reflectors,  those  of  about  twenty  inches  diameter  will 
be  referred  to.  It  is  supposed  that  the  two  lights  compared  are  con- 
structed so  as  to  present  the  same  distinguishing  features  ;  the  maxi- 


143 

mum  lustre  of  the  reflector  light  will  be  equal  only  to  1080  burners, 
with  other  disadvantages  ;  for  the  details  of  which,  reference  may  be 
made  to  M.  Fresnel's  note  No.  1,  section  two,  (hereto  annexed.)  M. 
Fresnel  remarks,  in  this  connection,  ' '  Without  pressing  further  the 
comparison  of  the  effects  of  the  two  kinds  of  apparatus,  we  will  per- 
ceive, without  doubt,  the  evident  advantages  of  the  dioptric  or  len- 
ticular combination,  which  in  fine  weather  will  not  present  an  absolute 
eclipse  at  a  less  distance  than  from  fifteen  to  eighteen  nautical  miles. 
If  we  now  consider  the  expenditures  of  oil,  we  will  find,  first,  that 
they  are  as  24  X  42  is  to  500,  or  as  1  to  2  ;  second,  that  the  economi- 
cal effects  will  be  as  2469  is  to  10,043,  or  as  1  to  4.07  :  thus  the  len- 
ticular apparatus  will  be  four  times  as  advantageous  as  the  reflector 
apparatus."  "Let  us  remark,  before  proceeding  further,  that  in 
employing  24  parabolic  reflectors,  of  about  20  inches  diameter,  for 
such  an  apparatus,  we  reach  the  utmost  possible*  limit,  without  ad- 
mitting the  employment  of  lanterns  of  a  size  beyond  all  proper 
bounds ;  and  we  may  also  affirm,  that  very  few  of  the  catoptric  lights, 
considered  as  lights  of  the  first  order •,  equal  the  lenticular  lights  of 
the  same  character  of  the  second  order. 

With  reference  to  the  first  order  dioptric  lights,  M.  Fresnel  re- 
marks, in  his  note  :  ' '  Now,  we  have  found  that  the  total  lustre  or 
brilliancy  of  an  apparatus  of  this  kind  is  equal  in  all  its  azimuths  to 
480  burners  of  Carcel.  But  it  will  be  practically  impossible  to  ob- 
tain a  like  effect  in  the  catoptric  system,  without  having  recourse  to 
the  employment  of  36  parabolic  reflectors  of  about  24  inches  diame- 
ter." "The  difficulty  becomes  still  greater,  if  it  be  necessary  to 
attain  with  these  reflectors  the  effect  of  a  revolving  lenticular  light, 
with  eight  large  lenses,  the  lustres  or  flashes  of  which  exceed  4,000 
burners  of  the  Carcel  lamp." 

"Let  us  limit  ourselves,  then,  without  entering  into  more  full  de- 
tails, to  the  observation,  that  the  economical  effect  of  a  fixed  light  of 
the  first  order,  illuminating  three-fourths  of  the  horizon,  is  to  the 
economical  effect  of  a  light  composed  of  parabolic  reflectors  of  about 
twenty-inches  diameter,  as  10,080  to  2,469,  or  as  4.08  to  1  :  that  is 
to  say,  that  the  first  will  be  (as  to  the  expense  of  the  oil  only)  four 
times  as  advantageous  as  the  second." 

With  regard  to  lights  varied  by  flashes  or  short  eclipse  lights,  "the 
catoptric  system  is  not  susceptible  of  producing  that  combination 
without  great  difficulty,  which  unites  to  the  permanence  of  fixed 


144 

lights  the  advantage  of  presenting  a  very  decided  character."      "No 
repairs  are  required  upon  the  lenticular  apparatus. 

The  amount  necessary  to  construct  and  put  into  operation  a 
"sideral"  light  for  harbor  purposes  may  be  stated  at  8,150  francs, 
or  about  $1,500;  and  the  annual  expense  for  its  maintenance,  in- 
cluding interest  upon  the  cost  at  the  rate  of  five  per  cent.,  at  1,207 
francs,  or  about  $225. 

The  amount  necessary  for  a  catadioptric  smaller  model  harbor  light 
may  be  put  down  at  9,181  francs,  or  about  $1,700;  and  the  annual 
expense  for  maintenance,  including  interest  of  first  cost,  £c.,  as 
above,  at  1,259  francs,  or  about  $235. 

The  useful  effect  of  the  "sideral"  light  has  been  found  equal  to 
68,400,  and  its  economical  effect  represented  by  57. 

The  useful  effect  of  the  catadioptric  light,  illuminating  three- 
fourths  of  the  horizon,  has  been  found  equal  to  137,700,  and  its  eco- 
nomical effect,  after  the  same  manner,  is  represented  by  109.  The 
comparison  of  these  two  will,  then,  be  in  the  proportion  of  57  to  109, 
or  as  1  to  1.91.  "Then,  besides  the  advantages  of  a  double  lustre, 
the  catadioptric  apparatus,  in  an  economical  point  of  view,  is  nearly 
twice  as  advantageous  as  the  catoptric  apparatus." 

M.  Fresnel  remarks  :  "It  is  difficult  to  establish  a  comparison  of  a 
precise  kind  between  the  fixed  lights  of  the  third  order  in  the  old 
and  the  new  systems,  because  we  cannot  obtain  with  the  ordinary 
parabolic  reflectors  a  passably  equal  distribution  of  light,  without 
multiplying  those  reflectors  to  such  a  number  as  would  require  a 
much  greater  expenditure  of  oil  than  could  be  allowed  for  lights  of 
that  class."  He  says  further  :  "I  will  merely  observe  that  I  have 
every  reason  to  believe,  from  the  indications  contained  in  the  table 
of  light-houses  of  the  United  States,  that  among  all  the  lights  of  that 
country  illuminated  by  reflectors,  the  diameters  of  which  do  not  ex- 
ceed sixteen  English  inches,  there  are  very  few  whose  useful  effect  is 
superior  or  equal  to  that  of  a  catadioptric  light  of  the  third  order 
larger  model." 

The  amount  necessary  for  establishing  a  reflecting  revolving  light 
with  twenty-four  parabolic  reflectors  of  about  twenty  inches  diameter, 
is  estimated  at  73,000  francs,  or  about  $13,700. 

Annual  expense  for  maintenance  of  the  same,  including  interest  at 
five  per  cent,  per  annum,  will  be  8,650  francs,  or  about  $1,625. 


145 

The  amount  necessary  for  establishing  a  second  order  revolving 
lenticular  light  is  estimated  at  105,500  francs,  or  about  $19,800. 

The  annual  expense  for  maintenance  of  the  same,  including  interest 
at  five  per  cent,  per  annum,  will  be  11,075  francs,  or  about  $2,075. 

The  useful  effect  of  the  reflector  light  is  represented  by  2,488,320, 
and  its  economical  effect  by  288. 

The  useful  effect  of  the  lenticular  light  is  represented  by  5,021,467, 
and  its  economical  effect  by  453. 

The  economical  effect  of  these  two  lights  will  then  be  represented 
by  288  and  453,  or  in  the  proportion  of  1  to  1.6.  "From  whence  it 
results  definitively  that  the  lenticular  light  of  the  second  order  will  be 
more  than  one  and  a  half  times  as  advantageous  as  the  catoptric  or  re- 
flector light,  which  we  may  without  doubt  consider  as  being  of  the  first 
order,  and  the  useful  effect  of  which,  nevertheless,  could  not  be  equal 
to  but  half  of  the  useful  effect  of  the  former." 

No  comparison  can  be  entered  into  between  the  first  order  len- 
ticular lights  and  reflector  lights,  for  the  reason  that  it  is  impossible 
to  construct  a  reflector  light  which  would  produce  a  sufficiently  pow- 
erful effect  to  be  compared  to  a  dioptric  one,  without  increasing  the 
dimensions  of  the  lantern,  and  the  number  and  size  of  the  reflectors, 
*to  a  degree  which  would  be  attended  with  a  very  great  expense,  and 
equally  great  inconvenience. 

From  the  foregoing  details,  which  have  been  drawn  mainly  from 
information  furnished  by  M.  Fresnel,  the  following  seems  to  be  but 
just  conclusions  : 

"1.  That  the  lights  fitted  with  the  dioptric  apparatus  present  a 
variety  in  their  power  and  effects,  and  may  be,  made  to  produce  an 
intensity  of  lustre,  which  render  them  of  an  interest,  in  a  nautical 
point  of  view,  incontestably  superior  to  those  fitted  with  the  catoptric 
apparatus.  • 

"2.  That  if  we  take  into  account  the  first  cost  of  construction  and 
the  expense  of  their  maintenance,  we  will  find,  with  respect  to  the 
effect  produced,  the  new  system  (dioptric)  is  still  from  once  and  a  half 
to  twice  as  advantageous  as  the  old,"  (reflector.) 

If  additional  arguments  and  evidence  were  wanting  to  establish 
the  now  almost  universally  conceded  fact,  of  the  very  positive  and  de- 
cided advantages  of  the  dioptric  system  of  Fresnel  over  all  other 
modes  of  illumination  for  light-houses,  they  might  be  found  to  exist 
at  present  in  an  unanswerable  form — that  of  the  practical  and  suc- 
10 


146 

cessful  application  of  the  system,  within  the  last  few  years,  in  nearly 
all  the  commercial  nations  of  the  world.  Prior  to  the  year  1832, 
there  was  not  a  single  dioptric  light  out  of  France;  and  on  the  French 
coast,  at  as  late  a  period  as  1834,  there  were  but  fourteen  large  and 
fifteen  small,  or  harbor  lights,  fitted  with  the  dioptric  apparatus. 

On  the  31st  December,  1845,  there  were  belonging  to  the  French 
light-house  department  one  hundred  and  twelve  lights  fitted  with  the 
dioptric  apparatus,  and  throughout  the  world  not  less  than  two  hun- 
dred and  ten  lights  fitted  upon  this  new  system  ;  one  hundred  of  which 
are  of  the  three  first  orders,  and  the  remaining  one  hundred  and  ten, 
small  or  harbor  lights,  without  including  apparatus  now  in  course  of 
construction  at  Paris,  to  which  allusion  has  already  been  made. 

The  objections  which  have  been  made  by  a  few  persons  to  the  em- 
ployment of  the  Fresnel  dioptric  apparatus  for  the  illumination  of 
light-houses,  in  consequence,  as  they  allege,  of  the  difficulties  which 
attend  the  management  of  the  mechanical  lamps  with  concentric  wicks, 
(which  are  absolutely  necessary  for  the  proper  illumination  of  the 
larger  orders  of  apparatus,)  seem  to  be  no  longer  tenable,  if  indeed 
there  ever  were  any  reasonable  grounds  of  objection  on  that  account. 

The  twenty-three  years'  experience  in  France,  (dating  from  the 
time  the  Cordouan  light  was  exhibited,)  where  ordinary  day  laborers 
are  taken  for  light-keepers,  and  the  undeniable  fact  of  the  successful 
employment  of  the  system  for  fourteen  years  in  Holland,  Scotland  and 
Norway  ;  for  from  five  to  ten  years  in  England,  Sweden,  Denmark, 
Prussia,  Belgium,  Spain,  Sardinia,  Tuscany,  Naples,  Brazils,  West 
Indies,  islands  of  the  Pacific  ocean,  Cape  of  Good  Hope,  <fec.,  must 
be  sufficient  evidence  to  convince  any  disinterested  and  unprejudiced 
mind  of  the  utter  folly  of  such  an  objection  at  the  present  day. 

In  a  communication  to  the  government  of  Norway  and  Sweden,  in 
1830,  M.  Fresnel  remarks  upon  this  subject :  "Happily,  an  experi- 
ence of  seven  years  has  dissipated  that  fear,  and  the  lenticular  lights 
have  been  distinguished  up  to  this  time  by  the  regularity  of  their  ser- 
vice." Again,  in  reference  to  the  same  subject,  M.  Fresnel  remarks, 
in  a  note  to  the  undersigned,  that  "opinions  thus  expressed  fifteen 
years  since,  based  upon  an  experience  of  seven  years,  have  been  great- 
ly strengthened  up  to  the  present  time,  embracing  a  period  of  twenty- 
two  years  since  the  establishment  of  the  Cordouan  light,  and  sustained 
by  the  results  daily  offered  of  more  than  one  hundred  and  ten  lights 
of  the  first  three  orders,  established  along  the  coasts  of  France  and 
different  foreign  powers."  "In  this  important  point  of  view,  then, 


147 

the  question  seems  to  be  irrevocably  settled  j  and  I  will  only  add  a 
few  considerations  relative  to  the  application,  more  or  less  extended, 
which  may  be  made  of  the  new  system  of  illumination  to  the  vast 
maritime  coasts  of  the  United  States." 

It  has  been  further  objected,  that  competent  persons  could  not  be 
procured  in  the  United  States  to  take  charge  of  the  lights  fitted  with 
the  dioptric  apparatus  and  mechanical  lamps,  for  the  salaries  at  pre- 
sent paid  to  light-keepers  of  the  existing  lights.  The  number  of 
keepers  necessary  for  those  lights  has  also  been  urged  as  an  objection 
to  their  introduction ;  and  there  is  also  a  third  objection,  emanating 
from  the  same  source,  that  the  mechanical  lamps  could  not  be  repair- 
ed when  employed  at  distant  or  isolated  points  on  the  coast. 

With  regard  to  the  keepers,  no  better  evidence  can  be  adduced 
than  the  opinions  of  M.  Fresnel  upon  the  subject,  and  the  practical 
results  furnished  daily  wherever  the  lights  are  employed.  M.  Fresnel 
says,  "that  the  difficulty  of  obtaining  proper  persons  to  fill  these  sub- 
altern stations  appears  to  be  most  singularly  exaggerated.77  "In 
France  they  belong  almost  always  to  the  class  of  ordinary  mechanics 
or  laborers,  who  make  from  one  and  a  half  to  two  and  a  half  francs  per 
day,  (from  27  to  46  cents.77)  "Eight  or  ten  days  will  suffice,  ordi- 
narily, to  instruct  a  light- house  keeper  in  the  most  essential  parts  of 
his  duty,  receiving  lessons  from  an  instructor  conversant  with  all  the 
details  of  the  service  ;  and  two  instructing  officers  will  be  sufficient 
to  prepare  keepers  for  all  the  lenticular  lights  which  could  be  succes- 
sively established  upon  the  coasts  of  North  America.77  "In  defence 
of  this  assertion,  I  will  cite  the  example  of  the  administration  of  Nor- 
way and  Sweden.77 

As  to  the  number  of  keepers  allowed  to  the  dioptric  lights,  there 
might  be  some  reason  in  the  objection,  if  it  were  possible  to  produce 
a  light  with  parabolic  reflectors  possessing  in  any  reasonable  degree 
the  advantages  arising  from  the  employment  of  a  first  order  catadiop- 
tric  apparatus  ;  but  as  it  is  well  established  that  reflectors  are  not 
susceptible  (practically)  of  any  combination  which  would  produce  a 
light  equal  in  every  respect  to  a  first  order  dioptric  light,  the  objec- 
tion ought  in  honesty  to  be  abandoned  or  waived  by  them,  Avithout 
they  prefer  bad  to  good  lights,  to  guide  the  mariner  in  his  perilous 
way  along  our  shores. 

The  lower  orders  of  dioptric  apparatus,  illuminated  by  ordinary 
Argand  lamps  and  burners,  with  single  and  double  wicks,  require  but 


148 

one  keeper  ;  and  they  produce  a  light  far  superior  to  those  of  the 
same  class  in  the  catoptric  system,  independently  of  the  economy  in 
the  use  of  the  dioptric  lights.  In  Scotland  and  in  England,  where 
the  lights  are  as  well  if  not  better  attended  than  in  any  other  parts 
of  the  world,  the  same  number  of  keepers  are  allowed  for  the  same 
class  of  lights,  without  regard  to  the  apparatus  employed,  whether 
catoptric  or  dioptric.  At  the  South  Foreland,  for  example,  there  are 
only  three  keepers  for  a  first  order  dioptric  and  a  first  order  reflector 
light,  placed  about  three  hundred  yards  apart ;  and  at  St.  Catherine's 
a  first  order  dioptric  light  has  but  two  keepers  to  attend  it ;  besides, 
other  instances  might  be  cited,  if  it  were  deemed  at  all  necessary. 
But  to  accomplish  in  the  most  perfect  manner  possible  the  great  and 
important  objects  for  which  lights  are  established  upon  seacoasts,  it 
would  seem  but  reasonable,  and  certainly  desirable,  rather  to  increase 
the  number  of  keepers  ordinarily  allowed  to  catoptric  lights,  than  to 
diminish  the  number  (taking  France  as  a  basis)  for  those  fitted  with 
dioptric  apparatus. 

In  regard  to  the  repairing  of  the  mechanical  lamps,  it  may  be  as- 
serted, without  the  fear  of  being  controverted,  that  in  consequence 
of  the  superior  manner  in  which  these  lamps  are  at  present  construct- 
ed in  Paris,  they  will  perform  well  for  a  number  of  years  by  bestow- 
ing upon  them  only  the  ordinary  attention  necessary  to  keep  them 
clean;  besides,  the  number  supplied  to  each  light-house  (from  3  to 
4.  and  never  less  than  3,)  is  a  sufficient  guarantee  against  any  acci- 
dents which  could  prevent  the  proper  exhibition  of  the  lights.  The 
same  objections  might,  with  equal  propriety,  be  urged  against  re- 
volving, flashing,  or  any  other  lights  requiring  clock  machinery  ;  yet 
such  lights  are  found  on  every  coast  where  lights  exist  to  any  extent. 
A  simple  inspection  of  the  works  of  a  mechanical  lamp  will  convince 
any  person,  of  common  understanding,  that  any  mechanic  who  is  ca- 
pable of  repairing  the  machinery  for  a  revolving  light  is  equally  com- 
petent to  put  in  order  any  lamp  used  in  light-houses,  and  particularly 
those  known  as  mechanical  lamps  with  concentric  wicks. 

The  oil  of  colza  is  used  exclusively  in  the  French  light-houses.  M. 
Fresnel  says  :  "From  numerous  experiments,  it  seems  to  me  that  these 
two  oils  ( spermaceti  and  colza )  may  be  employed  with  equal  success 
in  lamps  of  single  or  multiple  wicks" 

M.  Fresnel' s  preference  for  the  colza  (to  the  sperm  oil)  is  based 
upon  two  reasons  :  first,  the  colza  is  less  expensive  in  France  than 
sperm,  owing  to  the  fact  that  the  vegetable  from  which  this  oil  is 


149 

expressed,  is  cultivated  on  a  very  extended  scale  in  France,  Bel- 
gium, Holland,  Holstein,  &c.  j  and,  secondly,  the  great  difficulty  in 
detecting  impositions  which  may  be  and  are  practised  by  mixing  in- 
ferior oils  with  the  sperm,  while,  on  the  other  hand,  any  impurities 
in  the  colza  are  very  readily  detected.  No  experiments  have  yet 
been  made  in  France  to  test  fully  which  of  the  two  kinds  of  oil  will 
produce  the  best  light  for  light-house  purposes. 

******** 

There  is  but  one  floating-light  in  France  ;  that  is  constructed  of 
wood,  moored  and  illuminated  after  the  manner,  with  a  few  excep- 
tions, of  those  belonging  to  the  Trinity  Board  in  England.  The 
exceptions  are — first,  bronze  is  used  in  the  construction  of  the  lan- 
tern in  the  place  of  iron  ;  and,  secondly,  the  lamps  are  mechanical, 
the  pumps  of  which  are  put  in  play  by  springs,  instead  of  the  ordi- 
nary fountain  lamp.  This  latter,  in  spite  of  the  delicate  machinery 
of  the  lamp,  is  deemed  a  very  decided  improvement,  as  fulfilling 
much  more  fully  the  requirements  of  such  a  lamp,  by  preserving 
the  centre  of  gravity  in  the  same  vertical  during  the  whole  time  of 
the  combustion. 


HOLLAND. 

Ventilation  tubes  are  used  in  all  the  lanterns  to  conduct  off  the 
smoke  and  gasses  from  the  burners.  There  are  ventilators  in  the 
floor  and  sides  of  the  lanterns,  which  are  opened  and  shut  as  circum- 
stances require. 

The  general  opinion  is,  that  the  dioptric  system  of  Fresnel  is  pre- 
ferable to  the  catoptric  one  for  the  reasons  —  first,  the  superior 
quality  and  intensity  of  the  light  j  second,  economy  in  the  main- 
tenance when  a  great  arc  of  or  the  whole  horizon  is  required  to  be 
illuminated ;  third,  the  variation  which  can  be  given  to  the  revolv- 
ing lights  to  distinguish  the  one  from  the  other,  by  means  of  deter- 
mined eclipses,  either  short  or  long,  or  alternated  with  flashes,  and 
remaining  at  the  same  time  fixed,  visible  at  shorter  distances. 

The  large  number  of  officers  who  are  constantly  employed  by  the 
Netherlands  government  in  examining  the  condition  of  the  dikes, 
&c.,  on  the  seacoasts,  affords  ample  means  for  discovering  any  want 
of  efficiency  in  the  lights,  or  attention  to  the  duties  devolving  upon 
those  in  charge  of  them. 


150 


DANISH    LIGHT-HOUSES. 


A  due  regard  is  had  to  the  ventilation  of  the  lanterns,  to  prevent 
smoke,  insure  a  proper  combustion  of  the  oil,  and  a  pure  atmosphere 
for  the  keepers  to  breathe,  which  latter  has  been  of  the  greatest 
importance  in  preserving  the  health  of  those  whose  duty  requires 
them  to  spend  several  hours  of  each  night  in  an  atmosphere  which, 
without  that  precaution,  must  become  injurious  to  health,  to  say 

nothing  of  other  ill  effects,  such  as  producing-  an  inferior  light,  <fcc. 
*  *  *  TS-  *  *  *  -;:- 

Both  the  catoptric  and  dioptric  systems  are  in  use  at  present  in 
Denmark.  Prior  to  1842,  the  catoptric  system  only  was  used  ;  but 
since  that  period  seven  dioptric  and  catadioptric  lights  have  been  es- 
tablished, which  are  highly  approved  of. 

The  lenticular  apparatus  were  all  made  in  Paris  by  Mr.  Henry  Le- 
paute,  under  the  inspection  of  M.  Fresnel,  the  Engineer-inspector, 
Secretary  to  the  Commission  des  Phares  of  France,  and  put  up  in 
their  respective  towers  by  native  Danes,  who  had  had  the  opportu- 
nity of  seeing  similar  apparatus  put  up  in  Norwegian  light-houses. 


NORWEGIAN,    SWEDISH,     AND    RUSSIAN    LIGHT-HOUSE   ESTABLISHMENTS. 
*  -x-  *  *  •?:-  *  •?:-  * 

In  1830,  the  government  of  Norway  and  Sweden  addressed  a  com- 
munication to  the  French  light-house  commission  upon  the  subject 
of  the  improvement  of  its  lights.  In  1832,  the  light-house  at  the 
Isle  of  Oxoe  was  fitted  with  a  dioptric  apparatus,  the  manufacture 
of  Monsieur  Soleil,  senior,  of  Paris,  under  the  inspection  of  M. 
Leonor  Fresnel. 

The  next  dioptric  apparatus  for  that  coast  was  furnished  by  the 
same  distinguished  French  artist  in  1836,  and  placed  in  the  tower  at 
Gunarsborg.  Since  that  period,  dioptric  apparatus  have  been  annu- 
ally introduced  into  the  light-houses  of  Norway  ;  and,  at  the  present 
time,  there  are  not  less  than  fourteen  or  fifteen  of  the  different 
orders.  These  lights  were  fitted  up  by  French  mechanics,  and  the 
Norwegian  keepers  who  were  instructed  in  the  management  of  the 
French  mechanical  lamp  with  concentric  wicks.  All  lights  of  this 
description  are  now  fitted  up  and  attended  to,  exclusively,  by  natives 


151 

of  the  country ;  and  it  has  been  reported  that  no  difficulties  have 
been  encountered  in  any  of  the  details  relating  to  their  management 
which  required  foreign  aid. 

The  rape-seed  or  colza  oil  is  employed  in  these  lights.  The  usual 
means  are  employed  for  keeping  the  oil  in  a  limped  state  during  the 
cold  weather,  (stoves  and  frost  lamps.) 


PRUSSIAN    LIGHT-HOUSES. 


Of  the  eleven  Prussian  light-houses  at  present  in  operation,  two 
only  are  fitted  with  the  lenticular  apparatus  of  Fresnel  of  the  second 
order,  which  were  constructed  in  Paris.  The  nine  remaining  lights 
are  fitted  with  reflectors.  Sufficient  time  has  not  elapsed  since  the 
introduction  of  the  lens  lights  for  the  authorities  charged  with  their 
management  to  form  an  opinion  as  to  their  superiority  to  the  reflec- 
tors ;  yet  they  are  satisfied,  from  the  reports  of  those  familiar  with 
them,  that  they  are  greatly  superior  to  any  other  apparatus  for  light- 
house purposes. 


CHARACTER   OF   THE    FRENCH    LIGHTS. 

"Next  to  the  necessity  for  visibility  at  a  greater  or  lesser  distance, 
lights  ought,  as  far  as  possible,  to  present  characteristic  appearances 
by  which  to  distinguish  them  not  only  from  the  fixed  lights  which 
maybe  visible  in  the  same  horizon,  but  also  from  lights  situated  within 
the  limits  of  any  reasonable  errors  that  might  be  committed  by  navi- 
gators. That  announcement  would  seem  to  render  it  necessary  to 
discard  the  fixed  white  lights.  However,  as  the  revolving  lights  al- 
low of  but  a  small  number  of  sufficiently  marked  characteristics  ; 
and,  moreover,  as  the  fixed  lights  are  ordinarily  sufficiently  distin- 
guished by  their  elevation;  and  their  greater  brilliancy  of  light  than 
those  serving  for  the  illumination  of  the  interior  of  dwellings  and  of 
harbors,  we  have  introduced  this  description  of  light,  in  a  greater 
or  smaller  proportion,  into  the  whole  system  of  lighting  the  sea- 
coasts.'' 

"We  sometimes  have  recourse  to  double  fixed  lights,  for  the  purpose 
of  giving  to  them  a  very  decided  character  ;  for  example,  the  two 
lights  of  La  Heve,  near  the  port  of  Havre,  and  the  two  large  lights 


152 

which  are  in  the  course  of  construction  at  this  time  on  the  left  bank 
of  the  Canche,  in  the  department  of  the  Pas  de  Calais,  without 
speaking  of  the  double  small  lights  which  serve  to  mark  the  direc- 
tion of  the  channels  leading  to  ports  or  roadsteads." 

"Fixed  red  lights  (colored  by  the  application  of  red  glasses)  are 
doubly  objectionable:  first,  because  of  the  very  great  absorption  of 
the  rays  of  light  emitted  from  the  focus;  and,  secondly,  they  afford 
only  a  doubtful  character  to  the  light  during  the  existence  of  fogs, 
ivJien  all  lights  assume  a  reddish  tint.  This  mode  of  distinction  has 
not  been  employed  on  the  coast  of  France,  except  as  accessory,  and 
then  only  for  some  small  lights  situated  at  the  entrances  of  harbors, 
for  the  purpose  of  varying  the  appearance  of  some  changing  light." 

"Revolving  catoptric,  or  reflecting  lights,  are  distinguishable  generally 
only  by  the  greater  or  lesser  duration  of  their  eclipses,  which  be- 
come positive  often  at  the  distance  of  two  or  three  nautical  miles." 

•'This  mode  of  distinction,  which  would  seem  at  the  first  instant  to 
offer  a  great  variety  of  combinations,  is  in  reality  a  very  limited  one. 
On  one  side  we  cannot  extend  the  interval  of  time  between  two  con- 
secutive eclipses  to  three  minutes,  without  prolonging  beyond  proper 
limits  the  duration  of  the  eclipse,  during  which  time  the  navigator 
finds  himself  deprived  of  his  point  of  recognition  ;  and,  on  another 
side,  experience  proves  to  us  that  the  difference  of  thirty  seconds 
may  frequently  escape  an  inattentive  observer,  or  one  who,  in  bois- 
terous weather,  becomes  alarmed  at  his  supposed  dangerous  situa- 
tion." 

"The  inconvenience  arising  from  the  duration  of  the  eclipses  is 
scarcely  perceptible  with  the  revolving  dioptric  apparatus  upon  the 
new  model,  the  fixed  accessory  parts  of  which  reflect  a  light  con- 
stantly visible  in  a  horizon  extending  to  the  distance  of  nine  or  ten 
nautical  miles  with  an  apparatus  of  the  second  order,  and  with  those 
of  the  first  order  to  twelve  or  fifteen  nautical  miles." 

"The  different  combination's  of  changeable  dioptric  lights  at  pres- 
ent established,  are  as  follows  : 

First,  flashes  which  succeed  each  other  every  minute. 
Secondly,  flashes  which  succeed  each  other  every  half  minute. 
Thirdly,  alternate  white  and  red  flashes. 

Fourthly,  fixed  light,  varied  by  flashes  once  in  every  four  minutes. 
Fifthly,  fixed  light,  varied  by  flashes  once  in  every  three  minutes. 
Sixthly,  fixed  light,  varied  by  flashes  once  in  every  two  minutes. 


153 

Seventhly,  fixed  white  light,  varied  by  red  flashes  more  or  less 
frequent." 

"These  make  a  total  of  nine  principal  combinations.  It  is  proper 
to  remark,  besides,  that  the  first  three  combinations  have  been  ap- 
plied only  to  the  first  three  orders  of  lights,  conceiving  that  in  the  in- 
ferior orders  the  flashes  would  have  too  short  a  duration;  and  that 
the  eclipses  do  not  cease  to  be  positive,  but  at  too  short  a  distance 
from  the  light-house,  in  consequence  of  the  feebleness  of  the  fixed 
subsidiary  portion  of  the  apparatus." 


USEFUL   AND    ECONOMICAL   EFFECTS   OF   THE   DIFFERENT   LIGHTS. 

"The  useful  effect  of  a  light-house  apparatus  is  measured  by  the 
quantity  of  light  which  it  projects  upon  the  horizon. 

Observations  of  range  for  that  purpose  furnish  but  very  uncertain 
evidence,  on  account  of  the  difficulty  of  ascertaining  the  absolute 
range  of  a  light,  which  varies  according  to  the  state  of  the  atmos- 
phere, and  according  to  the  good  or  bad  sight  of  the  observer. 

To  arrive  at,  and  to  establish,  in  this  connection,  true  parallel  val- 
uations, it  is  indispensable  to  have  recourse  to  photometric  experi- 
ments. For  that  purpose,  having  taken  a  model  lamp  for  unity  of 
light,  (the  ordinary  lamp  of  Carcel,  for  example,)  receive  upon  a 
screen  fixed  at  a  proper  distance  the  two  shadows  projected  by  the 
same  style,  which  is  illuminated  at  the  time  by  the  apparatus  to  be 
measured,  and  by  the  lamp  of  unity.  The  latter,  placed  upon  a 
movable  stand  or  table,  is  moved  nearer  to  or  further  from  the 
screen,  until  the  two  adjacent  shadows  appear  of  an  equal  inten- 
sity, and  the  squares  of  the  distances  of  the  two  luminous  bodies  to 
the  screen  will  be  to  each  other  as  the  intensities  of  their  lights. 

To  measure  the  total  useful  effect  of  a  parabolic  reflector,  or  of  a 
plano-convex  lens,  we  may  proceed  in  the  following  manner  :  After 
having  placed  the  apparatus  in  the  centre  of  a  revolving  stand  or 
table,  fitted  with  a  movable  needle  and  a  graduated  circle,  measure 
the  intensity  of  the  light  in  different  azimuths  upon  the  whole  hori- 
zontal extent  of  the  luminous  cone  ;  take  the  mean  corresponding  to 
each  angular  extent ;  multiply  that  mean  by  the  number  of  divisions 
of  the  arc,  and  the  sum  of  all  these  partial  products  will  represent 
the  total  useful  effect.  The  mean  brilliancy  of  the  illuminated  sector 


154 

answers,  moreover,  to  the  quotient  of  the  useful  effect,  divided  by 
the  arc  which  measures  the  amplitude  of  that  sector. 

We  will  find,  lastly,  the  quantity  of  oil  expended  by  unity  of  light, 
and  per  hour,  in  dividing  the  total  useful  effect  by  the  number  of 
grammes  of  oil  consumed  in  an  hour,  and  the  quotient  will  represent 
the  economical  effect.* 

Photometric  measures  taken  in  this  manner  in  the  whole  illumin- 
ated angular  extent  of  a  revolving  apparatus,  make  known  the  max- 
ima and  minima  intensity  of  its  flashes,  and  from  which  we  deter- 
mine the  duration  of  their  apparitions,  by  dividing  by  the  entire  cir- 
cumference the  product  of  the  illuminated  arc,  multiplied  by  the 
duration  of  a  revolution. 

If  it  be  required  to  construct  with  parabolic  reflectors  an  appa- 
ratus for  a  fixed  light  to  illuminate  a  given  angular  extent,  we  must 
first  determine,  by  photometric  results,  the  number  of  reflectors 
necessary  to  distribute  in  the  extent  to  be  illuminated — if  not  uni- 
formly, at  least  in  a  complete  manner. 

Finally,  if  the  catoptric  apparatus  is  to  be  revolving,  it  is  easily 
ascertained  what  number  of  reflectors  are  to  be  placed  in  the  same 
plane  upon  each  face  of  the  movable  frame,  to  obtain  the  total  bril- 
liancy necessary." 

Useful  and  economical  effect  of  the  catoptric  apparatus. 

';  Catoptric  lights  are  so  varied  in  their  dimensions,  and  their  reflect- 
ing powers  at  the  same  time  so  variable,  according  to  the  degree  of 
perfection  in  their  fabrication,  (without  adverting  to  the  differences 
in  the  calibres  of  the  lamp  burners,)  that  it  will  be  very  difficult  to 
present,  with  any  degree  of  certainty,  the  table  of  useful  effects  to 
the  principal  lights  of  that  system  at  present  in  use  on  the  coasts  of 
England,  the  United  States,  and  of  France. 

I  will  limit  myself  here  to  some  indications  relative  to  lights  of 
this  description,  which  I  have  at  my  disposition.  I  will  remark, 
once  for  all,  that  the  unity  of  light  to  which  all  the  photometric  results 
which  may  be  given  hereafter  have  been  referred,  is  the  ordinary 
burner  of  a  Carcel  lamp,  burning  42  grammes  (1  oz.  7.73  drachms) 
of  the  oil  of  colza  per  hour." 

*  Whenever  the  economical  effect  of  two  lights  is  to  be  compared,  it  is  not  sufficient  to 
take  simply  the  expenses  of  the  oil.  It  will  be  necessary  to  estimate  their  annual  ex- 
pense, and  divide  it  by  the  amount  of  light  usefully  expanded  upon  the  horizon,  in  the 
manner  hereafter  described. 


155 


"(A.) — Photophore  (reflector)  with  an  aperture  of  50  centimetres, 
(19.69  inches,)  and  a  depth  of  20  centimetres,  (7.876  inches,)  illumi- 
nated by  a  lamp  burning  42  grammes  (1  oz.  7.73  drachms  avoirdu- 
pois) per  hour  of  oil. 


BRILLIANCY  OR  LUSTRE. 

AZIMUTHS. 

OBSERVATIONS 

Correspond- 

ing to  the 

MEANS. 

divisions. 

In  Burners. 

In  Burners. 

10° 

2 

i  f\ 

The  brilliancies  or  lustres  measured  at  equal 

8° 

18 

1U 

31 

distances  to  the  right  and  to  the  left  of  the  axis 

6° 

44 

have   presented  differences  sufficiently  remark- 

40 

74 

59 

able  ;    but  uniformity  has  been  established  by 

20 

160 

91  & 

taking  the  means.     No  account  has  been  taken 

00 
20 
40 

270 
160 
74 

zio 
215 
117 
59 

of  the  brilliancy  of  the  simple  burner  beyond 
10°  ;  so  that  the  amplitude  of  the  luminous  cone 
has  been  computed  as  reduced  to  20°. 

60 

44 

31 

80 

18 

100 

2 

10 

864 

This  sum  represents  the  useful  effect  for  the  uni- 

form divisions  of  every  20°. 

Useful  effect,  corresponding  (as  is  ordinarily  done)  to  the  division  of 
the  circle  into  minutes,  in  this  case=864  burners Xl20'=:103, 680. 

O  /I  A 

Mean  lustre  or  l)rilliancy=. =86.4  burners. 

Maximum  lustre  or  brilliancy  corresponding  to  the  cm's:=270  burners. 

Economical  e/ect=1^^ 

42  grammes=2,469. 


156 

(B.) — Photophore  (reflector)  with  an  aperture  of  0.275  metre, 
(10.83  inches,)  and  a  depth  of  12  centimetres,  (4.72  inches,)  illumi- 
nated by  a  lamp  burning  35  grammes  (1  oz.  3.75  drachms)  of  oil  per 
hour. 


BRILLIANCY  OR  LUSTRE. 

AZIMUTHS. 

Correspond- 

ANGULAR 
DISTANCE. 

PRODUCTS. 

OBSERVATIONS. 

ing  to  the 

MEANS. 

divisions. 

Burners. 

Burners. 

16° 
150 
Uo 
120 
100 
80 
60 
00 

2 

4 
6 
12 

18 
27 
48 
(56 

3 
5 
9 
15 
22.5 
37.5 
57 

10 

10 

20 
2o 
20 
20 
60 

3 
5 
18 
30 
45 
75 
342 

As  the  divisions  are  un- 
equal, it  has  been  found 
necessary  to  multiply  each 
mean  lustre  or  brilliancy 
by  the  angular  space  cor- 
responding to  it. 

518 

Useful  effect,  corresponding  to  the  division  in  minutes,  in  this  in- 
stance, is  =  2x518xGO'=62,160. 

518 

Mean  lustre  or  l)rilliancy>=. — r=32.4  burners. 
16 

Maximum  lustre  or  brilliancy  corresponding  to  the  axis— 66  burners. 

Economical  effect— 62'160 

35  grammes=:l,776. 

(C.) — "Sideral"  reflector  of  Bordier  Marcet,  formed  of  two  para- 
bolic metallic  mirrors,  with  a  diameter  of  0.344  metre,  (13.54  inches,) 
and  an  aperture  of  0.187  metre,  (7.364  inches,)  illuminated  by  a 
lamp  burning  50  grammes  (1  oz.  12.25  drachms  avoirdupois)  of  oil 
per  hour. 

Uniform  brilliancy  or  lustre  in  all  the  azimuthsizi4  burners.  The 
extent  illuminated,  after  deducting  the  spaces  occupied  b}~  the  lamp 
and  the  frame,  is  about  285  degrees,  or  17,100  minutes. 

Useful  e/ect=4:  x  17, 100=68,400. 

Economical  e/ect= — ~~=  1 » 8  6  8 . 


157 

The  foregoing  results  confirm  the  following  principles,  the  evidence 
of  which  springs  moreover  from  a  simple  enunciation  of  them : 

1st.  The  useful  effect  of  a  parabolic  reflector  increases  with  its  di- 
mensions and  with  that  of  the  illuminating  body. 

2d.  The  economical  effect  of  a  reflector  of  given  dimensions  is  great- 
est when  the  lamp-burner  is  smallest. 

3d.  The  divergence  is  greatest  when  the  flame  is  most  voluminous, 
or  when  the  reflector  is  smallest.  We  cannot,  then,  (all  other  things 
being  equal,)  augment  the  economical  effect  of  a  reflector,  without  di- 
minishing its  useful  effect — that  is  to  say,  without  reducing  its  bril- 
liancy or  intensity,  and  consequently  its  range.  The  reduction  of 
the  volume  of  light  within  certain  limits  is  particularly  objectionable 
when  it  appertains  to  eclipse  apparatus,  in  which  case  it  limits  the 
width  of  the  luminous  cone,  and  consequently  augments  the  length 
of  the  eclipses.*  The  same  reduction  applied  to  the  crowns  (foci)  of 
reflectors  composing  a  fixed  light  apparatus,  may  weaken  the  light 
in  their  intervals  to  such  a  degree  as  to  produce  dead  angles,  or  be- 
come completely  obscured  to  the  observer  beyond  certain  distances. 

It  is  further  proper  to  remark  that  the  horizontal  divergence  is 
not  lost  for  useful  effect,  but  that  the  divergence  in  the  vertical  sense 
only  profits  the  navigator  in  the  limited  angular  space  comprised  be- 
tween the  tangent  at  the  surface  of  the  sea  and  the  ray  terminating 
at  the  distance  of  some  miles  from  the  light. 

Finally,  there  is  for  the  calibre  of  the  lamp-burners  applicable  to 
reflectors  of  given  dimensions,  and  destined  for  the  illumination  of  an 
equally  determined  range,  a  maximum  beyond  which  prodigality  of 
light  ensues,  and  a  minimum  within  which  the  illumination  becomes 
insufficient." 

Useful  and  economical  effect  of  dioptric  apparatus. 

"Before  commencing  an  analysis  of  the  effect  of  the  light  of  the 
lenticular  or  dioptric  apparatus,  I  will  state — 

First,  That  these  lenses  always  contain,  independently  of  the  fixed 
or  movable  dioptric  drum,  a  subsidiary  catoptric  or  catadioptric  part, 
the  useful  effect  of  which  is  combined  with  that  of  the  principal  part. 

0  It  was  to  obviate  the  defect  of  divergence  that  Bordier  Marcet  invented  his  large 
double  parabolic  reflectors  with  double  focus ;  but  that  combination  caused  too  great  a  loss 
of  light. 


158 

Second.  That  when  these  lenses  are  not  required  to  illuminate  the 
whole  of  the  horizon,  that  side  which  remains  deprived  of  light  is 
fitted  with  spherical  reflectors  (metallic)  in  place  of  the  dioptric 
drum,  which  adds  about  one-fifth  to  the  intensity  of  the  sector 
directly  corresponding. 

That  being  stated,  I  now  proceed  to  present  the  photometric 
results  obtained  from  different  lenses  of  the  four  orders  of  dioptric 
apparatus. 

[Lenticular  apparatus  of  the  first  order.] 


(A.} — First  order  lenticular  apparatus  for  a  fixed  light,  with  accessory 
catoptric  part.  * 

Lustre  or  brilliancy  of  the  dioptric  drum  =360  burners. 
Mean  brilliancy  of  mirrors — 

7  upper  zones=80  )  _12Q  burnprs 
4  lower  zones  =  40  j- 

Total  amount  of  brilliancy=480        " 


Calculation  of  the  useful  effect. 

1st.  The  dioptric  drum  illuminating  equally  the  whole 
of  the  horizon,  (except  about  26°,  being  computed 
the  amount  of  space  occupied  by  the  frames  of  the 
apparatus,  and  that  of  the  lantern, )=360  burn- 

ersx20,000'  = 7,200,000 

2d.   7  zones  of  upper  mirrors  =80  burners  X  20, 000'=  •  •     1,600,000 
3d.   4  zones  of  lower  mirrors,  omitted  for  one-eighth  of 
the   circumference,   for  the  necessary  passage  of 
the  keepers,=  40  burners X 17, 500'= 700, 000 

Total  of  useful  effect 9,500,000 

ci  •     i    «•    *      9,500,000 

Economical  effect  =  -- 

750     gramrnes=  12,667. 

0  Notwithstanding  the  decided  adv.xi,tages  which  the  catadioptric  zones  present,  com- 
pared to  the  mirrors,  we  may,  by  reason  of  their  economy,  prefer,  under  some  circum- 
stances, the  second  combination  to  the  first  for  lenticular  apparatus  of  the  first  order. 


159 

If  the  apparatus  illuminate  only  three -fourths  of  the  cir- 
cumference of  the  horizon,  the  useful  effect  will  be  re- 
duced to 7,200,000 

To  which  must  be  added  the  effect  of  the  reflector  occu- 
pying the  vacant  space  in  the  dioptric  drum,  one -fifth 
(360  burners  X  5, 000'=: 360, 000 

Useful  effect  of  the  apparatus,  for  270°= 7,560,000 

7,560,000 

1st  order,  economical  effects ^r^- —  1A  AOA 

750      grammesr=10,080 


(a1) — First  order  lenticular  apparatus  for  a  fixed  light,  luith  accessory 
catadioptric  part. 


Lustre  or  brilliancy  of  the  dioptric  drum 360  burners. 

Cupola  or  upper  zones=:. 140  burners  )  9AA        tl 

Lower  zones= 60       "        J 

Total  brilliancy 560 


Calculation  of  the  useful  effect. 

560  burners  X  20, 000'= 11,200,000 

From  which  must  be  deducted  for  the  passage  of  the 

keepers,  60  burners X  2, 500'=. 150,000 

Remainder  of  useful  effect= 11,050,000 


11,050,OCO 
Economical   effect  =—^50"     grammes  =  14,733. 

If  the  apparatus  illuminate  only  three-fourths  of  the  cir- 
cumference of  the  horizon,  the  useful  effect  becomes 
reduced  to  560  burners x  15, 000'= 8,400,000 

To  which  must  be  added,  as  in  the  other  case,  for  the 
advantages  of  the  reflector  occupying  the  open  space 
in  the  dioptric  drum,  one-fifth  (360  burners  X  5, 000')=:  360,000 

Useful  effect  of  the  apparatus,  for  270° 8,760,000 

8,760,000 
Economical    effect  =  •  — 720~~grammeB  =  11,680. 


160 


(a?) — First  order  revolving  lenticular  apparatus,  with  accessory  catop- 
tric part. 

Brilliancy  or  lustres,  measured  upon  one-half  of  the  amplitude  of 
the  luminous  beam,  emitted  from  a  lens  of  one  metre  (39.38  inches) 
in  height,  and  occupying  a  space  of  45°: 


Brilliancy  or  Lustre. 

Answering  to 

the  divisions 

BURNERS. 

BURNERS. 

210' 

4(?) 

77 

The  annexed  brilliancies  of  light  are  the  results 

180' 

150 

of  means  of  different  experiments. 

150' 
120' 
90' 

800 
2,000 
2,900 

1,400 
2,450 
3  300 

It  is  just  to  remark  that  all  the  divisions  have 
intervals  of  thirty  minutes,  BO  as  to  distribute, 
in  effect,  the  partial  products  of   the  mean 

GO' 
30' 

3,700 
3,  900 

3,800 

intensities  into  the  angular  distances. 

0' 

4,200 

4,050 

15,552 

The  useful  effect  of  a  lens  =  2  x  15,552  X  30'=  933,120 


Ditto of  the  8  lenses  of  a  dioptric  drum 

Ditto of  11  zones  of  mirrors,  as  before  •  • 


Total  useful  effect 

9,764,960 
Economical    effect  —  -—w^. — 

7oO      grammes  =  13, 020. 


*7,464,960 
2,300,000 

9,764,960 


If  the  apparatus  illuminate  only  three-fourths  of  the  horizon,  the 
useful  effect  will  be  reduced  to  7,758,720;  and  the  economical  effect 
to  10,345. 


°  We  have  given  7,200,000  to  the  dioptric  drum  of  a.  fixed  UgM—a.n  amount  which  seems 
satisfactory,  in  consideration  of  the  degree  of  uncertainty  attending  photometric  opera- 
tions. 


161 


(b)— Second  order  lenticular  apparatus  for  a  fixed  light,  with  a  catadi- 
optric accessory  part.* 

Lustre  or  brilliancy  of  the  dioptric  drum  = 160  burners. 

Upper  part,  or  cupola  = 76 

Lustre  or  brilliancy  of  the   catadioptric  zones — lower 

zones  = 28 

Total  lustre  or  brilliancy  in  burners 264 


Calculation  of  useful  effect. 

264  burners  x  20, 000'= 5, 280, 000 

From  which  must  be  deducted  for  the  space  of  one-sixth 
of  the  circumference,  which  is  not  supplied  with  the 
catadioptric  zones  below  the  lenticular  drum 93,333 


Remainder  of  the  useful  effect  =: 5, 186, 667 

5,186.667 


Economical    effect  = 


500      grammes  =  10, 373. 


If  the  apparatus  illuminate  only  five-sixths  of  the  circumference 
of  the  horizon,  a  reflector  is  placed  on  the  side  of  the  earth;  the 
useful  effect  then  becomes  reduced  to  4,706,667,  and  the  economical 
effect  to  9,413. 

For  an  illumination  embracing  only  three-fourths  of  the  circum- 
ference of  the  horizon,  the  useful  effect  is  then  reduced  to  4,120,000, 
and  the  economical  effect  to  8,240. 

(ty) — Second  order   revolving  lenticular  apparatus,    with  catadioptric 
accessory  part. 

The  lustres  or  brilliancies  measured  upon  half  of  the  amplitude  of 
the  luminous  beam  emitted  from  a  lens  of  80  centimetres  in  height, 
occupying  a  space  of  30  degrees. 

*  For  the  second  order  (and  with  greater  reason  for  the  inferior  orders)  we  dispense  with 
the  use  of  the  concave  mirrors  for  the  subsidiary  part  of  the  apparatus.  The  increased  use- 
ful effect  of  that  part  which  is  always  faced  is,  above  all,  important  in  the  revolving  dioptric 
drum  apparatus  to  prevent,  at  a  certain  distance,  the  complete  disappearance  of  the  light 
or  positive  eclipses. 
11 


162 


Brilliancy  or  Lustre. 

Azimuths. 

Angular 
distances. 

Products. 

Observations. 

Answering  to 
the  divisions. 

Means. 

BUBNEBS. 

210' 
180' 
150' 
120' 
90' 
60' 
0' 

3(?> 
61 
274 
492 
907 
933 
1,080 

32(?) 
167.5 
383 
699.5 
920 
1,006.5 

30' 
30' 
30' 
30' 
30' 
60' 

960 
5,025 
11,490 
20,985 
27,600 
60,390 

126,450 

Useful  effect  of  a  lens  2  X  126,450  =  252,900. 

Useful  effect  of  12  lenses  of  the  drum 3,034,800 

Useful  effect  for  catadioptric  zones 1,986,667 


Total  useful  effect  == 5,021,467 

5,021,467 

grammes  =  10,043. 


Economical    effect  =  • 


500 


(c) — Lenticular  apparatus  for  a  fixed  light  of  the  third  order  (larger 
size)  ivith  catadioptric  accessory  part. 

Brilliancy  of  the   dioptric   drum  =  50  burners  :    brilliancy  of  the 

catadioptric  dome  or  cupola  —  20  burners;  total  —  70  burners. 
Useful  effect  =  70  burners  X  20,000'=  1,400,000. 
1,400,000 

190      grammes  =  7, 368. 


Economical   effect  = 


If  the  apparatus  illuminate  only  four-fifths  of  the  circum- 
ference of  the  horizon,  the  useful  effect  is  reduced  to-  •  •  1,120,000 
To  which  add  for  spherical  reflector 40, 000 


Total  useful  effect  = 1, 160, 000 

1,160,000 

Economical   effect—      -.^ —  „  nr.c 

190      grammes  =  6, 105. 

Catadioptric  apparatus  of  the  third  order  (smaller  size)  for  a  fixed  light. 
Brilliancy  of  the  apparatus  =  31  burners. 
Useful  effect  =  31  burners  x  20,400'  =  632,400. 

632,400 

Economical   effect  =  — ^-? — 

115    grammes  =  54,999. 


163 

If  the  apparatus  illuminate  only  three-fourths  of  the  circumference 
of  the  horizon,  the  useful  effect  will  be  reduced  to  474, 300,  and  the 
economical  effect  to  124. 

It  must  bo  remembered  that  this  apparatus  may  be  illuminated 
with  a  decided  advantage  by  means  of  an  ordinary  Argand  lamp  with 
one  ivick,  with  which  we  will  obtain  the  following  results: 
Brilliancy  of  the  apparatus  =  25  burners.* 
Useful  effect  =  25  x  20,400'  =  510,000. 

510,000 

Economical   effect .  =  — «TT~ 

60      grammes  —  8,500. 

Fourth  order  catadioptric  apparatus  for  a  fixed  light  (larger  model) 

Brilliancy  of  the  apparatus  =.  15  burners. 
Useful  effect  =  15  X  20,400'=:  306,000. 
v  .    ,     „    .       306,000 

~4— grammes  =5, 100. 

If  the  apparatus  illuminate  only  three-fourths  of  the  horizon,  the 
useful  effect  will  become  reduced  to  229,500.  and  the  economical 
effect  to  3,825. 

Fourth  order  catadioptric  apparatus  (smaller  model)  for  a  fixed  light. 

Brilliancy  of  the  apparatus  =  9  burners. 
Useful  effects  9  X  20,400'=  183,600. 

183,600 

Economical   effect  =  -45— grammes  =  4>  080. 

If  the  apparatus  illuminate  only  three -fourths  of  the  circumference 
of  the  horizon,  the  useful  effect  becomes  reduced  to  137,700,  and  the 
economical  effect  to  3,060. 

General  observations  upon  photometric  measures. 

The  photometric  results  from  which  I  have  deduced  the  values  of 
the  useful  effects  and  of  the  economical  effects  of  the  various  orders  of 
catoptric  and  dioptric  apparatus  should  only  be  considered  as  simple 
approximations.  New  experiments  upon  apparatus  of  the  same  kind 

°The  catadioptric  apparatus  of  50c.  (19.69  inches)  diameter,  illuminated  thus  by  an 
ordinary  constant  level  lamp,  burning  60  grammes  (2  ounces  1.9  drachm  avoirdupois)  of 
oil  per  hour,  offers  a  very  advantageous  combination  for  the  illumination  of  the  entrances 
to  ports  and  roadsteads,  with  ranges  of  12  to  15  nautical  miles.  One  keeper  is  sufficient  to 
perform  with  ease  all  the  service ;  and  the  ordinary  annual  expenti  does  not  exceed  (in  France)  one  thou- 
sand to  eleven  hundred  francs  ($187.  50  to  $206.25.  ) 


164 

would  show,  without  doubt,  very  remarkable  differences,  not  only 
because  of  the  greater  or  lesser  precision  which  the  construction  of 
the  optical  pieces  may  present,  and  of  the  difficulty  of  obtaining  the 
identity  of  brilliancy,  in  the  unity  of  light,  but  also  in  consequence 
of  the  nature  of  the  photometric  experiments,  where  it  becomes  neces- 
sary to  estimate  by  the  eye  the  equal  intensities  of  shadows  produced 
by  light,  often  of  different  tints. 

These  approximations  are  always  sufficient  to  establish  results  exact 
enough  between  the  effects  of  the  different  illuminating  apparatus  to 
be  compared,  and  give  much  more  correct  ideas  as  to  their  relative 
values  than  can  be  deduced  from  observations  upon  the  absolute  range 
of  the  lights. 

Service  of  the  Catoptric  lights. 

The  fixed  catoptric  lights  established  upon  land,  and  illuminated  by 
a  small  number  of  reflectors,  say  from  six  to  eight,  may  be  attended 
by  a  single  keeper,  especially  if  he  be  assisted  by  his  family.  If  the 
apparatus  be  a  revolving  one,  or  if  the  number  of  reflectors  be 
greater  than  six  or  eight,  it  will  become,  ordinarily,  necessary  to 
employ  two  keepers,  as  well  to  superintend  the  light  during  the 
night,  as  to  maintain  in  a  proper  manner  the  illuminating  apparatus 
and  fixtures.  If  the  light  be  placed  in  an  isolated  position  at  sea, 
three  keepers  at  the  least  are  necessary  to  assure  regular  attendance. 
In  such  cases,  these  agents  (keepers)  are  relieved  at  regular  intervals, 
and  permitted  to  return  to  the  continent  for  fifteen  days  or  a  month. 

Service  of  the  Lenticular  lights. 

The  lenticular  lights  of  the  fourth  order,  and  of  the  third  order 
smaller  model,  require  but  a  single  keeper  to  superintend  them, 
except  in  cases  when  situated  at  isolated  points  at  sea. 

Two  keepers  are  required  to  superintend  the  lights  of  the  third 
order  larger  model,  and  the  second  order,  in  consequence  of  the  use 
of  the  mechanical  lamps  in  those  lights. 

Three  keepers  are  required  for  the  superintendence  of  lights  of  the 
first  order. 

For  lights  of  the  second  and  third  orders,  in  isolated  positions  at 
sea,  it  is  necessary  to  employ  three  keepers,  and  four  keepers  for  lights 
of  the  first  order  similarly  situated. 


165 

COMPARISON  OF  THE  TWO  SYSTEMS  OF  LIGHTS. 
Parallel  beticeen  the  Catoptric  and  Dioptric  lights. 

The  preceding  developments  have  appeared  to  nie  indispensable, 
as  preliminaries  to  the  establishment  of  a  parallel  between  the  two 
systems  of  illuminating  light-houses. 

I  will  consider  the  two  systems  under  the  following  heads : 

1st.  The  absolute  useful  and  economical  effects. 

2d.  The  first  cost  of  the  establishment,  and  of  the  repairs  and  main- 
tenance. 

3d.  The  facility  and  safety  of  the  service. 

Apparatus  of  the  fourth  order,  smaller  model. 

SEC.  1.  Absolute  useful  and  economical  effect  of  the  illuminating  appa- 
ratus.— The  brilliancy  of  a  catadioptric  apparatus  of  30c.  (11.8  inches) 
interior  diameter,  illuminated  by  a  lamp  burning  45  grammes  (one 
ounce,  nine  and  four-tenths  drachms  avoirdupois)  of  oil  per  hour,  has 
been  found  equal  to  eight  or  nine  burners. 

The  brilliancy  of  a  "sideral"  reflector,  illuminated  by  a  lamp  burn- 
ing 50  grammes  (one  ounce,  twelve  and  tiventy-flve  hundredths  drachms 
avoirdupois)  of  oil  per  hour,  is  equal  to  four  burners.  This  brilliancy 
of  the  first  is  at  least  double  that  of  the  second. 

The  useful  effect  of  the  catadioptric  apparatus  of  the  fourth  order, 
illuminating  three-fourths  of  the  circumference  of  the  horizon,  is 
represented  by  137,700.  The  useful  effect  of  the  "sideral"  reflector 
is  equivalent  to  68,400.  Comparison  of  the  second  to  the  first  =:  1 
to  2.  Economical  eifect  of  the  catadioptric  apparatus  =  3060. 
Economical  effect  of  the  "sideral"  reflector  ==  1368.  Comparison 
of  the  second  to  the  first  =  1  to  2.24.  If  we  take  for  a  term  of  com- 
parison the  ordinary  reflector,  (a  coquille  plate, )  the  superiority  of  the 
catadioptric  apparatus  will  be  still  more  decided.  With  regard  to 
the  concave  parabolic  reflectors,  or  " photophores,"  I  will  not  introduce 
them  into  this  parallel,  in  consideration  that  they  can  only  serve  in 
isolated  cases  for  the  ordinary  .illumination  of  the  entrances  to  har- 
bors, upon  an  amplitude  of  not  more  than  twenty  degrees. 

Apparatus  of  the-  third  ordet,  smaller  model. 

The  apparatus  of  the  third  order,  smaller  size,  illuminated  by  an 
ordinary  fountain,  or  constant  level  lamp,  carrying  one  burner  and  one 


166 

wick,  consuming  60  grammes  (two  ounces  one  and  nine-tenths  drachm 
avoirdupois)  of  oil  per  hour,  or  one  burner  with  t ico  wicks,  consuming 
115  grammes  (four  ounces  and  one  drachm)  of  oil  per  hour,  have  no 
equivalents  in  the  catoptric  apparatus  in  use  at  present. 

A  "sideral"  apparatus,  of  the  same  useful  effect,  would  be  of  a 
dimension  which  would  render  the  construction  of  it  very  difficult 
and  very  expensive,  and  would  require,  relatively,  a  very  great  con- 
sumption of  oil.  Neither  could  we  supply  it  in  a  proper  manner  by 
the  use  of  parabolic  reflectors,  except  they  were  made  expressly  for 
the  purpose,  of  very  small  dimensions,  to  allow  a  sufficient  number 
to  distribute  properly  the  light  upon  three-fourths  of  the  horizon. 
It  is  evident,  moreover,  that  that  embarrassing  combination  would 
require  a  consumption  of  more  than  200  grammes  (7  ounces)  of  oil 
per  hour. 

The  old  light  of  Cette.  (Herault.)  provisionally  illuminated  by  a 
eatadioptric  apparatus  of  50  centimetres  (19.69  inches)  diameter, 
with  a  lamp  of  two  concentric  wicks,  is  easily  seen,  in  ordinary 
weather,  at  the  distance  of  15  to  18  nautical  miles,  although  it  is 
given  a  range  in  the  official  table  of  only  12  nautical  miles. 

Apparatus  of  the  third  order,  larger  model. 

The  brilliancy  of  catadioptric  apparatus  of  the  third  order,  one 
metre  (39. 38  inches)  in  diameter  in  the  interior,  illuminated  by  a 
mechanical  lamp  of  double  wick,  burning  190  grammes  (6  oz.  11.35 
drachms)  of  oil  per  hour,  has  been  found  =  70  burners.  I  will  sup- 
pose, moreover,  that  it  embraces  only  four-fifths  of  the  horizon. 

To  illuminate,  by  means  of  reflectors,  the  same  angular  space  of 
238-.  with  an  effect  of  light  about  equal,  it  will  be  necessary  to  employ 
14  parabolic  reflectors  (photophores)  of  57. 5c.  (10.8  inches)  diameter, 
each  burning  35  grammes  (1  oz.  3.8  drachms)  of  oil  per  hour.  The 
brilliancy  in  the  axis  of  each  of  the  14  reflectors  will  be  about  =  66 
burners.  The  brilliancy  in  the  intervals,  the  least  illuminated,  will 
be  =  36  burners.  The  useful  effect  will  be  represented  by  14  x 
62,160  =  870,240.  But  the  useful  effect  of  the  catadioptric  appa- 
ratus has  been  found  to  be  =  1, 160,000.  In  this  case,  notwithstand- 
ing the  very  great  difference  in  the  consumption  of  oil,  the  dioptric 
or  lenticular  apparatus  is  superior,  in  useful  effect,  to  the  catoptric 
apparatus.  The  economical  effect  of  the  first  apparatus  is  repre- 
sented by  1786 :  comparison  =1  to  3.44  :  that  is  to  say,  without 
estimating  the  expenditure  of  oil  by  unity  of  light,  the  lenticular 


167 

apparatus  will  be  nearly  three  and  a  half  times  more  advantageous 
than  the  catoptric  apparatus.  With  regard  to  the  effective  expendi- 
ture of  oil,  it  will  be  in  the  proportion  of  190  grammes  to  14x35 
grammes,  or  of  1  to  2.6. 

Apparatus  for  a  fixed  light,  second  order. 

The  brilliancy  of  a  catadioptric  apparatus  of  the  second  order, 
having  an  interior  diameter  of  1m.  40c.  (4  feet  7. 13  inches)  illumi- 
nated by  a  mechanical  lamp  of  three  concentric  wicks,  burning  five 
hundred  grammes  (17  oz.  10.5  drachms)  of  oil  per  hour,  has  been 
found  to  be  =  264  burners.  Let  us  suppose  it  only  embraces  three- 
fourths  of  the  horizon.  To  obtain  an  effect  about  equal  in  an  angular 
space  of  270°,  it  will  be  necessary  to  employ  at  least  thirty-four 
parabolic  reflectors,  having  fifty  centimetres  (19.69  inches)  diameter. 
The  brilliancy  in  the  axis  of  each  of  these  thirty-four  reflectors  will 
be  =:  270  burners.  But  the  lustres  in  the  intervals  are  only  =  148 
burners.  The  useful  effect  of  the  catadioptric  apparatus  will  be 
4,120,000,  and  that  of  the  thirty-four  reflectors  by  34x103,680  = 
3,525,120.  The  comparison  between  the  absolute  expenditure  of  oil 

34  X  42 
will  be  =  — .  „„      =,  2.86  to  1 ;  and  the  comparison  of  the  quantity 

of  oil  expended  by  unity  of  light  =  £±££  =  1  to  3.33  ;  thus,  in  this 
last  respect,  the  lenticular  apparatus  will  be  three  and  one-third 
times  as  advantageous  as  the  catoptric  apparatus. 

Revolving  apparatus  of  the  second  order. 

The  maximum  brilliancy  or  lustre  of  the  revolving  apparatus  of  the 
second  order,  with  twelve  lenses,  has  been  found  to  be  :=  1,184 
burners,  as  follows : 

1st.  Brilliancy  in  the  axis  of  a  lens  =. 1,080  burners. 

2d.    Brilliancy  in  the  fixed  catadioptric  zones  = 104       " 


Total  amount  of  brilliancy  = 1, 184 

And  the  minimum  corresponding  to  the  eclipses,  is  equivalent  to  one 
hundred  and  four  burners. 

To  construct  a  catoptric  apparatus,  possessing  an  equivalent  effect, 
without  multiplying  beyond  bounds  the  reflectors,  (photophores,)  it 
will  be  requisite,  without  doubt,  to  take  those  with  diameters  of 
fifty-five  centimetres  to  sixty  centimetres  (21.66  inches  to  23.63 
inches;)  but  for  want  of  sufficiently  precise  data  as  to  their  lustres, 


168 

I  will  suppose  the  employment  of  reflectors  of  fifty  centimetres 
(19.69  inches)  diameter,  which  give,  in  their  axis,  a  lustre  equal  to 
two  hundred  and  seventy  burners.  I  will  suppose,  also,  that  the 
frame  has  six  faces,  each  fitted  with  four  of  these  reflectors.  I  will 
admit,  lastly,  as  the  succession  of  flashes  ought  to  be  the  same  in 
both  systems,  that  the  lenticular  apparatus  makes  its  revolution  in 
six  minutes,  and  the  catoptric  apparatus  in  three  minutes.  The 
maximum  lustre  of  the  catoptric  system  will  be  equal  to  4  X  270  = 
1,080  burners.  The  amplitude  of  the  lustres  of  the  reflectors  being, 
moreover,  of  sixteen  degrees  at  most,  there  will  be  six  angles  of 
forty-four  degrees  each  almost  entirely  obscured :  and  the  length  of 
these  eclipses  will  be  twenty-two  seconds,  while  the  length  of  the 
flashes  will  be  only  eight  seconds. 

Without  pressing  further  the  comparison  of  the  effects  of  the  two 
kinds  of  apparatus,  we  will  perceive,  without  doubt,  the  evident 
advantages  of  the  dioptric  or  lenticular  combination,  which,  in  fine 
weather,  will  not  present  an  absolute  edipse  at  a  less  distance  than 
fifteen  to  eighteen  nautical  miles.  If  we  now  consider  the  expendi- 
ture of  oil,  we  will  find — 

First.  That  they  are  as  24x42  :  500,  or  :  :  1  to  2  ; 

Second.  That  the  economical  effects  will  be  as  2,460:  10,043,  or 
as  1  to  4.07. 

Thus  the  lenticular  apparatus  will  be  four  times  as  advantageous 
as  the  catoptric  or  reflector  apparatus. 

I  admit  that  this  result  might  be  modified  by  the  employment  of 
larger  reflectors  ;  but  as  their  divergence  would  be  less,  the  length 
of  the  flashes  would  be  diminished,  and  consequently  that  of  the 
eclipses  would  be  augmented  too  much. 

Let  us  remark  before  proceeding  further,  that  in  employing  25 
parabolic  reflectors  (photophores)  of  50  centimetres  (19.69  inches) 
diameter  for  such  an  apparatus,  we  reach  the  utmost  possible  limit, 
without  admitting  the  employment  of  lanterns  of  a  size  beyond  all 
proper  bounds  ;  and  we  may  also  affirm  that  very  few  of  the  catop- 
tric lights,  considered  as  lights  ofihejirst  order,  equal  the  lenticular 
lights  of  the  same  character  of  the  second  order. 

Apparatus  of  the  first  order. 

With  the  view  not  to  multiply  unnecessarily  the  comparisons,  I 
will  omit  the  details  relative  to  the  first  order  of  the  catadioptric 
combination,  which  is  the  most  advantageous;  and  I  will  suppose,  in 


169 

consequence,  the  lenticular  apparatus  fitted  in  its  accessory  part  with 
eleven  zones  of  fixed  mirrors.  Now,  we  have  found  that  the  total 
lustre  or  brilliancy  of  an  apparatus  of  that  kind  is  equal  in  all  its 
azimuths  to  480  burners.  But  it  will  be  practically  impossible  to 
obtain  a  like  effect  in  the  catoptric  system,  without  having  recourse 
to  the  employment  of  36  reflectors  with  apertures  (diameters)  of  60 
centimetres  (23.63  inches.) 

The  difficulty  becomes  still  greater  if  it  be  necessary  to  attain  with 
these  parabolic  reflectors  the  effect  of  a  revolving  lenticular  light 
with  eight  large  lenses,  the  lustres  or  flashes  of  which  exceed  4,000 
burners  of  the  Carcel  lamp. 

Let  us  limit  ourselves,  then,  without  entering  into  more  full  details, 
to  the  observation  that  the  economical  effect  of  a  fixed  light  of  the  first 
order,  illuminating  three-fourths  of  the  horizon,  is  to  the  economical 
effect  of  a  light  composed  of  parabolic  reflectors  ("  photophores")  of 
50  centimetres  (19.69  inches)  diameter  as  10.080  to  2.469,  or  as  4.08 
to  1.  That  is  to  say,  that  the  first  will  be  (as  to  the  expense  of  oil 
only)  four  times  as  advantageous  as  the  second. 

Apparatus  for  lights  varied  by  flashes. 

I  will  only  here  refer  to  the  apparatus  for  lights  varied  by  flashes, 
(otherwise  called  of  short  eclipses,)  for  the  purpose  of  remarking  that  the 
catoptric  or  reflector  system  is  not  susceptible  of  producing,  without 
great  difficulty,  that  combination  which  unites  to  the  permanence  of 
fixed  lights  the  advantage  of  presenting  a  very  decided  character. 

SEC.  2.  Expenses  offlrst  establishing  and  of  maintaining  light-houses. — 
So  far,  I  have  compared  the  economical  effects  of  the  different  kinds 
of  apparatus  only  with  reference  to  the  expenditures  of  oil ;  but  it 
will  not  fail  to  be  objected  that  the  advantages  which  I  point  out  in 
favor  of  the  lenticular  system  ought  to  be  very  greatly  diminished  in 
a  fiscal  point  of  view,  in  consequence  of  the  high  price  of  the  appa- 
ratus, and  the  excess  of  keepers  necessary  to  their  service.  To 
appreciate  the  value  of  that  objection,  I  will  compare  several  lights 
of  both  systems,  taking  into  the  account  all  the  expenses  to  which 
they  could  be  subjected,  and  for  the  first  example  I  will  take  the 
harbor  lights. 

HARBOR    LIGHTS. 

A  harbor  light,  placed  at  the  entrance  to  a  port,  being  often  ex- 
posed to  the  force  of  the  sea,  ought  (to  insure  proper  attendance,  &c.) 


170 

to  be  erected  securely  in  a  bronze  lantern,  fitted  upon  the  summit  of 
a  small  tower  constructed  of  masonry,  and  sufficiently  spacious  for 
the  purposes  of  illumination  and  attendance  at  all  times,  and  in  every 
description  of  weather. 

That  being  established,  we  may  state  the  expenses  for  the  first 
establishing  for  both  systems,  (in  France,)  as  follows  : 

1.  Small   "sideral"   light. 

Small  tower  in  masonry 5, 000  fr. 

Octagonal  lantern,  1m.  40c.  (4  feet  7. 13  inches)  in  diameter. .   2,  G50 
"Sideral"   reflector,  with  subsidiary  pieces 500 


=  $1,528  12.  8,150 


Interest  at  5  per  cent 407  fr. 

Annual  expense  of  the  service 800 


=  $226  31.  1,207 


2.    Catadioptric  harbor  light,  (smaller  model.) 

Tower  and  lantern 7, 650  fr. 

Catadioptric  apparatus 1,531 


=  $1,721  43.  9,181 


Interest  at  5  per  cent , 459  fr. 

Annual  expense  of  the  service 800 


=  $236  06.  1,259 


The  useful  effect  of  the  ' '  sideral"  (reflector)  light  having  been  found 
equal  to  68,400— 

68,400 

Its  economical  effect  will  be  represented  here  by =  57. 

1,207 

The  useful  effect  of  the  Catadioptric  light,  illuminating  three-fourths 
of  the  horizon,  has  been  found  to  be  equal  to  137,700 — 

137,700 

After  the  same  manner,  its  economical  effect  will  be =109. 

1,259 

The  comparison  of  the  economical  effects  of  these  two  will  be,  then, 
in  the  proportion  of  57  to  109,  or  1  to  1.91. 


171 

Then,  besides  the  advantage  of  a  double  lustre  or  brilliancy,  the 
catadioptric  apparatus,  in  an  economical  point  of  view,  is  nearly 
twice  as  advantageous  as  the  catoptric  apparatus. 

Lights  of  the  third  order. 

It  is  difficult  to  establish  a  precise  comparison  between  the  fixed 
lights  of  the  third  order  in  the  old  and  in  the  new  system,  because 
Ave  cannot  obtain  with  the  ordinary  parabolic  reflectors  a  passably 
equal  distribution  of  light,  without  multiplying  these  reflectors  to  such 
a  number  as  would  require  a  much  greater  expenditure  of  oil  than 
could  be  allowed  for  lights  of  that  class. 

I  will  merely  observe  that  I  have  every  reason  to  believe,  from  the 
indications  contained  in  the  table  of  light-houses  in  the  United  States, 
that  among  all  the  lights  of  that  country  illuminated  by  reflectors, 
the  diameters  of  which  do  not  exceed  sixteen  English  inches,  there 
are  very  few  whose  useful  effect  is  superior,  or  even  equal  to  that  of 
a  catadioptric  light  of  the  third  order,  larger  model. 

[Revolving  lights  of  the  second  order  ] 

1st.  Catoptric  light. 

In  the  comparative  examination  of  the  useful  and  economical  effects  of 
the  two  systems  of  maritime  illumination,  I  have  supposed  the  re- 
volving catoptric  apparatus  of  the  second  order,  composed  of  twenty- 
four  parabolic  reflectors  of  fifty  centimetres  (19.69  inches)  of  aperture 
distributed  equally  upon  the  six  faces  of  prismatic  frame.  I  will  sup- 
pose, also,  that  the  lantern  is  three  metres  (9  feet  10.14  inches)  in 
diameter,  the  same  as  required  for  a  lenticular  apparatus  of  the  sec- 
ond order,  but  with  a  little  less  height.  I  will  admit,  moreover,  the 
same  perfection  in  the  works — that  is  to  say,  that  the  frame  and  sashes, 
constructed  of  iron,  are  covered  with  bronze  exteriorily  ;  and  that 
the  roof  or  dome  of  the  lantern  is  of  copper,  the  glazing  of  glass  of 
eight  or  ten  milimetres  (0.39  to  0.31  of  an  inch)  in  thickness,  <fec. 

With  regard  to  the  buildings,  the  only  remarkable  difference  will 
consist  in,  that  the  catoptric  light-house  will  require  room  to  lodge 
two  keepers,  while  I  will  estimate  for  three  in  the  lenticular  light- 
house. That  being  stated,  the  necessary  expenses  to  be  incurred  in 
the  first  system  may  be  approximately  estimated  as  follows  : 


172 

Light-house  tower,  <fec 50, 000  fr. 

Octagonal  lantern,  three  metres  (9  ft.  10.14  inches)  in 
diameter,  dressed  in  bronze 10,500 

Illuminating  apparatus,  consisting  of  twenty-four  reflec- 
tors, fifty  centimetres  (19.69  inches)  in  diameter,  re- 
volving frame,  rotary  machinery,  <fcc 12,500 


Total  first  cost 
=$13,687  50. 


Interest  at  five  per  cent 3,  G50  fr. 

Annual  expense  of  the  service,  estimating  the  oil  at  the 
highest  price 


Total  annual  expense 
=$1,621  87. 


2(7.   Revolving  lenticular  apparatus  of  the  second  order. 

Light-house   tower,  &c 60, 000  fr. 

Lantern  and  subsidiary  fixtures 12,500 

Catadioptric  lenticular  apparatus  and  mechanical  lamps-      33,000 


Total  first  cost 105,500 

=$19,781  25.  

Interest  at  five  per  cent 5, 275  fr. 

Annual  expense  of  the  service   5, 800 


Total  annual  expense  • 11,075 

=$2,076  56.  = 

The  useful  effect  of  twenty-four  parabolic  reflectors  of  fifty  centime- 
tres (19. 69  inches)  diameter  will  be  equal  to  24x103,680=2,488,320. 

Cy     AOO     QOfl 

The  economical  effect  will  be  represented  by  -      .1,      =288. 

o,  650 

The  useful  effect  of  a  lenticular  light  of  the  second  order,  with 
twelve  revolving  lenses,  has  been  valued  at  5,021,467. 

The  economical  effect  will  then  be  represented  by  5'°12|;_4.67  =453. 

1 1,  0  i  o 

The  economical  effects  of  these  two  lights  will  then  be  in  the  pro- 
portion of  288  to  453,  or  of  1  to  1.6.  From  whence  it  results  defi- 
nitely, that  the  lenticular  light  of  the  second  order  will  be  more  than 
one  and  a  half  times  as  advantageous  as  the  catoptric  light,  which  we 


173 

may  without  doubt  consider  as  being  of  the  first  order,  and  the  useful 
effect  of  which,  nevertheless,  could  not  be  equal  to  but  the  half  of  the 
useful  effect  of  the  first. 

Lights  of  the  first  order. 

I  find  myself  arrested  in  the  attempt  to  make  a  comparison  of  the 
catoptric  and  dioptric  lights  of  the  first  order,  for  the  reason  that  we 
could  not,  without  increasing  beyond  all  proper  limits  the  number  of 
reflectors  and  the  dimensions  of  the  lantern,  construct  a  catoptric 
apparatus  to  produce  a  sufficiently  powerful  effect  to  be  assimilated 
to  a  dioptric  apparatus  of  the  first  order.  I  mention  this  in  this 
place  merely  that  it  may  not  be  forgotten. 

From  the  preceding  details  we  may  conclude  : 

1st.  That  the  lights  fitted  with  the  dioptric  apparatus  present  a 
variety  in  their  power  and  in  their  effects,  and  may  be  made  to  pro- 
duce an  intensity  of  lustre  which  renders  them  of  an  interest  in  a 
nautical  point  of  view,  incontestably  superior  to  those  fitted  with 
the  catoptric  apparatus. 

2d.  That  if  we  take  into  account  the  first  cost  of  construction,  and 
the  expense  of  their  maintenance,  we  will  find,  in  respect  to  the 
effect  produced,  the  new  system,  (dioptric)  is  still  from  once  and  a 
half  to  twice  as  advantageous  as  the  old. 


FACILITY   AND    SECURITY    OF   THE   SERVICE   OF   THE    LIGHT-HOUSES   OF   THE 
OLD   AND   NEW   SYSTEMS. 

After  having  balanced  the  advantages  relative  to  the  two  systems 
of  lights  in  view  of  their  useful  and  economical  effects,  I  ought  to  con- 
sider them  with  reference  to  their  security  and  the  facility  with  which 
they  are  served. 

I  will  reproduce,  upon  this  subject,  the  observations  inserted  in  a 
memoir  of  the  20th  of  April,  1830,  in  which  I  replied  to  the  ques- 
tions which  were  addressed  to  me  by  the  government  of  Sweden  and 
Norway,  in  relation  to  the  necessary  measures  to  be  taken  to  improve 
the  lighting  of  its  maritime  coast. 

"The  service  of  lenticular  lights  is,  in  the  aggregate,  less  labo- 
rious than  that  of  the  reflector  lights.  The  first,  demand  at  all  times 
during  the  night  the  unremitted  attention  of  the  keeper.  If,  for  ex- 
ample, the  central  lamp  should  become  extinct  during  the  absence  of 


174 

the  keeper  from  the  lantern,  or  while  he  is  asleep,  the  horizon  of  the 
light  would  remain  some  hours  plunged  in  total  darkness,  and  the 
greatest  objection  which  has  been  urged  against  our  new  s}'stem  of 
illumination  is  the  fear  of  such  accidents.  Happily,  an  experience 
of  seven  years  has  dissipated  that  fear,  and  the  lenticular  lights  have 
been  distinguished  up  to  this  time  by  the  regularity  of  their  service. 
However,  every  precaution  has,  besides,  been  taken  to  replace 
promptly  the  lamp  or  its  burner  in  case  of  extinction.  The  extreme 
simplicity  of  the  day  duty  compensates  the  keepers  for  that  to  which 
they  are  subjected  during  the  night.  To  snuff  and  replace  the  wicks, 
renew  the  oil,  sweep  the  chambers  of  the  lantern  and  the  stairs  of 
the  tower,  dust  the  apparatus,  and  sometimes  wash  with  a  little 
spirits  of  wine  the  tarnished  spots  upon  it,  and,  lastly,  to  wipe  dry 
the  glass  of  the  lantern — such  is  the  principal  daily  duty  which  is 
divided  between  the  keepers  of  the  new  lights,  and  which  rarely  occu- 
pies them  more  than  two  hours." 

Opinions  thus  expressed  fifteen  years  since,  based  upon  an  expe- 
rience of  seven  years,  have  been  greatly  strengthened  up  to  the 
present  time,  embracing  a  period  of  twenty-two  years  since  the  estab- 
lishment of  the  Cordouan  light,  and  sustained  by  the  results  daily 
offered  of  more  than  one  hundred  lenticular  lights  of  the  three  first 
orders,  established  along  the  coasts  as  well  of  France  as  of  different 
foreign  powers. 

In  this  important  point  of  view,  then,  the  question  seems  to  be 
irrevocably  settled,  and  I  will  only  add  a  few  considerations  relative 
to  the  application,  more  or  less  extended,  which  may  be  made  of  the 
new  system  of  illumination,  to  the  vast  maritime  coasts  of  the  United 
States. 

1st.  It  has  been  objected  that  it  would  require  too  great  sacrifices 
to  be  made  to  procure  in  that  country  keepers  possessing  the  amount 
of  intelligence  requisite  for  the  superintendence  of  lenticular  lights. 
2d.  That  from  distant  points  or  stations  the  necessary  repairing 
and  renewing  of  the  mechanical  lamps  would  be  attended  with  great 
difficulty. 

I  will  reply,  with  regard  to  the  keepers,  that  the  difficulty  of  ob- 
taining proper  persons  to  fill  these  subaltern  station^  appears  to  be 
most  singularly  exaggerated.  In  France  they  belong  almost  always 
to  the  class  of  ordinary  mechanics,  or  laborers,  who  make  from  1.50 
francs  to  2.50  francs  (27  to  46  cents)  per  day. 

Eight  or  ten  days  will  suffice,  ordinarily,  to  instruct  a  light-keeper 


175 

in  the  most  essential  parts  of  his  duty,  receiving  lessons  from  an 
instructor  conversant  with  all  the  details  of  the  service  ;  and  two 
instructing  officers  will  be  sufficient  to  prepare  keepers  for  all  the 
lenticular  lights  which  could  be  successively  established  upon  the 
coasts  of  North  America.  The  information  thus  imparted,  would 
never  be  lost ;  and  these  officers  might,  besides,  be  aided  by  fore- 
men or  assistants,  who  could  supply  the  place  in  case  of  necessity. 
In  defence  of  this  assertion,  I  will  cite  the  example  of  the  adminis- 
tration of  Norway  and  Sweden,  which,  after  having  obtained  the 
assistance  of  a  French  agent  to  put  up  the  apparatus  of  the  two  first 
lenticular  lights,  which  were  sent  from  Paris  in  1832  and  1836,  has 
provided  since,  without  any  foreign  assistance,  for  the  placing,  as 
well  as  the  organization  of  the  service,  of  all  the  lights  of  the  new 
system  which  it  has  successively  established. 

With  reference  to  the  eventual  repairs  of  the  mechanical  lamps,  it 
is  to  be  considered— 

1st.  That,  in  consequence  of  the  great  strength  of  the  pieces  of 
which  the  new  model  of  mechanical  lamps  are  composed,  they  will 
perform  well  for  a  number  of  years  without  requiring  anything  more 
than  a  proper  attention  to  their  cleanliness. 

2d.  That  the  ordinary  assortment  of  a  dioptric  light-house  com- 
prises three  of  these  lamps,  which  afford  a  sufficient  guarantee  against 
the  chances  of  accident ;  and  besides,  we  may,  by  increasing  a  little 
the  mean  expense,  increase  the  number  to  four  under  some  circum- 
stances, as  an  exception  to  the  general  rule. 

3d.  That  the  repairs  of  the  implements  under  discussion  may  be 
easily  made  by  all  the  clock  or  watchmakers,  or  other  mechanicians, 
to  whom  we  have  recourse  for  repairing  the  revolving  machinery  of 
light-houses. 

I  conclude  with  the  remark,  that  if  it  be  determined  to  multiply 
the  application  of  the  new  system  of  maritime  illumination  in  the 
United  States,  it  seems  to  me  that  it  will  be  expedient  to  engage  one 
of  the  foremen  employed  in  the  manufactory  of  our  mechanical  lamps  to 
go  to,  and  remain  in  the  country  for  several  years.  By  that  measure, 
which  would  be  attended  with  very  little  expense,  all  the  difficulties 
which  might  present  themselves  at. first  in  establishing  lenticular 
lights  would  be  removed,  and  the  perfect  regularity  of  the  service 
of  these  new  establishments  would  be  insured. 

LEONOR  FRESNEL. 

PARIS,  December  31,  1845. 


176 


FRANCE. 

Extract  from   Parliamentary   report,    1834. — Licjld-ltouse  service  of 

France. 

The  light-houses,  for  the  most  part,  existing  on  the  coast  of  France 
before  the  revolution,  had  been  built  and  were  managed  by  commer- 
cial bodies. 

A  law  of  the  National  Assembly,  dated  the  loth  September,  1792, 
centralized  the  light-house,  beacon,  buoy,  and  sea-mark  service,  by 
placing  it  under  the  superintendence  of  the  Minister  of  Marine,  and 
by  charging  the  Minister  of  the  Interior  with  the  execution  of  the 
\vorks  agreed  upon  for  this  service  by  the  two  departments. 

A  consular  order,  dated  the  llth  June,  1802,  confirmed  the  law  of 
loth  September,  1792,  concerning  light-houses. 

An  imperial  decree  of  the  7th  March,  1805,  caused  the  light-house, 
buoy,  .sea-mark,  and  beacon  service  to  be  attached  to  the  official 
duties  of  the  Minister  of  the  Interior,  and  from  that  time  they  were 
placed  under  the  immediate  direction  of  the  commissioners  of  roads 
arid  bridges.  This  decree,  nevertheless,  requires  the  Ministers  of 
the  Interior  and  of  Marine  to  advise  with  each  other  in  reference  to 
the  establishment  of  any  new  light-houses  or  sea-marks;  and  this  ar- 
rangement gave  rise  to  the  light-house  commission,  which  was  estab- 
lished in  1811. 

In  1825,  at  which  period  the  system  of  lenticular  lights  was  defi- 
nitely adopted  for  lighting  the  coast  of  France,  this  commission  is 
found  to  have  been  composed  as  follows : 

M.  Becquey,  councillor  of  State,  director  general  of  roads  and 
bridges,  president  of  the  commission. 

M.  De  Prony,  inspector  general  of  roads  and  bridges,  member  of 
the  Institute. 

M.  Tarbe  de  Vaux  Glairs,  inspector  general  of  roads  and  bridges, 
councillor  of  State. 

M.  Sparkin,  inspector  general  of  hydraulic  works  at  the  seaports. 

M.  Holland,  inspector  general  of  naval  architecture. 

M.  Halgar,  rear  admiral  and  councillor  of  State. 

M.  De  Rossel,  rear  admiral,  director  of  the  repository  of  charts  and 
plans  of  the  royal  navy,  member  of  the  Institute. 


177 

M.  Beautemps  Beaupre.  Hydrographer-in-chief  of  the  royal  navy, 
member  of  the  Institute. 

M.  Arago,  Astronomer,  member  of  the  Institute. 

M.  Mathieu,       do.  do.  do. 

M.  Fresnel,  (late  Augustin,)  principal  engineer  of  roads  and 
bridges,  member  of  the  Institute,  secretary  of  the  light-house  com- 
mission. 

It  was  by  this  commission  that  all  the  projects  and  measures 
adopted  since  its  institution  for  the  improvement  of  the  light-house 
and  sea-mark  service  were  examined  and  discussed,  and  one  of  its 
most  important  labors  was  the  study  and  examination  of  the  general 
system  adopted  in  1825,  upon  the  report  of  Rear  Admiral  de  Rossel, 
for  lighting  the  coasts  of  France. 

Present  organization  of  the  light-house  service. 

The  organization  of  the  light-house  service  of  France,  now  in 
force,  is  briefly  as  follows: 

This  service  is  attached  to  the  official  duties  of  the  Minister  Sec- 
retary of  State  for  the  Department  of  the  Interior,  and  is  altogether 
under  the  direction  of  the  Councillor  of  State  charged  with  the  gen- 
eral administration  of  the  roads  and  bridges. 

In  each  naval  district,  the  prefect,  principal  engineer,  assistant 
engineers,  and  the  superintendents  of  pouts  et  chaussees,  direct  or 
supervise,  in  the  sphere  of  their  respective  offices,  all  that  relates 
to  the  management  of  light-houses,  sea-marks,  and  beacons  in  the 
neighborhood. 

The  light-house  service,  considered  collectively,  embraces  light- 
ing, reparatory  works,  and  the  formation  of  new  establishments. 

Beparatory  ivorks. — The  repair  or  restoration  of  light-houses,  after 
being  authorized  by  the  director  general,  is,  with  the  roads  and 
bridges  works,  executed  under  the  superintendence  of  the  district 
administration. 

New  establishments.— In  the  formation  of  new  establishments,  the 
following  routine  is  observed  : 

The  engineers  of  the  district,  where  the  new  edifice  is  about  to  be 
erected,  make  a  draught  of  the  plan,  in  conformity  with  the  basis 
previously  determined  on  by  the  light-house  commission. 

This  plan  is  forthwith  submitted  to  the  commission,  which  confines 
12 


178 

itself  to  the  inquiry  as  to  whether  the  wants  of  the  service,  nauti- 
cally  or  otherwise  reported  on,  and  constituting  the  main  objects, 
have  been  complied  with. 

It  is  then  presented  to  the  council  of  roads  and  bridges  to  receive 
their  estimate,  founded  on  the  reports  made  of  tbe  architectural  ar- 
rangements of  the  system  of  building,  and  of  the  calculated  expense. 
After  receiving  the  approbation  of  the  director  general  of  roads  and 
bridges,  and  of  the  Minister  of  the  Interior,  the  plan  is  sent  to  the 
prefect  of  the  district,  who  proceeds  to  the  public  adjudication  (con- 
tract) of  the  works,  and  intrusts  the  engineers  with  the  execution  of 
them. 

The  lamps  and  light  apparatus  are  made  at  Paris,  under  the  care 
of  the  engineer-in  chief,  secretary  to  the  light-house  commission. 

The  establishment  of  new  light-houses  is  announced  to  the  public 
:vro  or  three  months  beforehand,  by  means  of  bills  and  advertise- 
ments inserted  in  the  maritime  newspapers. 

TLe  administration,  moreover,  publishes  annually  a  summary  de- 
scription of  the  light-houses  and  lights  on  our  coasts,  and  causes  five 
r  .-ix  thousand  copies  to  be  distributed  among  French  and  foreign 
navigators. 

The  whole  of  the  expenses  (with  the  exception  of  the  cost  of  light- 
ing a  very  small  number  of  lights  of  purely  local  interest)  connected 
with  the  light-house  service  are  supplied  from  the  public  treasury. 
The  administration  of  the  customs  of  France  does  not  levy  any 
special  light-house  duty  upon  maritime  commerce.  This  duty, 
which  was  abolished  by  the  law  of  the  18th  October.  1793,  is  at  the 
present  time  compounded  with  the  tonnage  duty  which  all  vessels 
pay  upon  their  arrival  in  port.  LOR.  FREIXEL, 

Secretary  of  the  Light-house  Commission. 

PARIS,  Apr  ff  30. 


List  of  the  French  Light-house  Commission  in   1851,  instituted  April. 

1811. 

The  Minister  of  Public  Works,  or  in  his  absence  the  under  Secre- 
tary of  State  presides  during  the  sittings  of  the  commission. 

M.  Arago,  commander  in  the  Legion  of  Honor,  representative  of 
the  people,  member  of  tbe  Institute  and  of  the  bureau  of  longitudes- 


179 

M.  Mathieu,  Knight  in  the  Legion  of  Honor,  member  of  the  In- 
stitute and  of  the  bureau  of  longitudes. 

M.  Mathieu,  Commander  in  the  Legion  of  Honor,  rear-admiral. 

M.  De  Hell,  High  officer  in  the  Legion  of  Honor,  rear-admiral,  en 
retraite. 

M.  Leroux.  Commander  in  the  Legion  of  Honor,  general  inspector 
of  maritime  engineering. 

M.  Trette  de  Laroche,  Officer  in  the  Legion  of  Honor,  divisionary 
inspector  of  bridges  and  roads,  charged  with  the  general  inspection 
of  maritime  works. 

M.  Fresnel.  Officer  in  the  Legion  of  Honor,  divisionary  inspector  of 
bridges  and  roads,  en  retraite. 

M.  Reynaud,  Knight  in  the  Legion  of  Honor,  chief  engineer  of 
bridges  and  roads,  secretary. 

List  of  the  Trinity-House  Board,  London. — Elder  Brethren  in  1851. 

Duke  of  Wellington,  K.  G.,  Master. 

Captain  Sir  J.  H.  Pelly,  Deputy  master. 

Captain  Aaron  Chapman. 

Right  Hon.  Lord  Viscount  Melville,  K.  T. 

Captain  Robert  Welbank. 

Captain  John  Hayman. 

Captain  Henry  Nelson. 

Admiral  Sir  T.  Byam  Martin,  G.  C.  B. 

Captain  Charles  Weller. 

Right  Honorable  Sir  J.  R.  G.  Graham,  Bart. 

Right  Honorable  Earl  of  Minto,  G.  C.  B. 

Captain  Frederick  Maden. 

Admiral  Sir  Charles  Adam,  K.  C.  B. 

Captain  Stepheuson  Ellerby. 

H.  R.  H.  Prince  Albert,  K.  G. 

Captain  George  Probyn. 

Captain  William  Pixley. 

Captain  Charles  Farquharson. 

Captain  Robert  Gordon,  R.  X. 

Captain  William  E.  Farrer. 

Captain  Henry  Bonham  Box. 

Right  Honorable  Earl  of  Haddington. 

Most  Honorable  Marquis  Dalhousie. 

Captain  John  Shepherd. 


180 

Captain  Edward  Foord. 

Captain  Gabriel  J.  Redman. 

Right  Honorable  Lord  J.  Russell,  M.  P. 

Captain  John  Fulford  Owen. 

Capt.  David  James  Ward. 

Right  Honorable  H.  Labouchere,  M.  P. 

Capt,  Wm.  Pigott. 

Jacob  Herbert,  Esq.,  Secretary. 


TRANSLATION. 
[Ministry  of  Pullic  Works — Second  Bureau — Navigation — Light-houses.] 

Control  of  the  consumption  of  oil,  and  of  the  condition  of  the  different 

supplies. 

PARIS,  March  17.  1845. 

SIR  :  The  great  expense  incurred  by  the  administration  for  the 
purpose  of  carrying  the  illumination  of  our  maritime  coasts  to  a  de- 
gree of  perfection  which  will  insure  the  safety  of  navigators,  will 
riot  fulfil  perfectly  that  object  if  the  service  is  not,  on  the  part  of 
the  engineers,  an  object  of  their  special  care  and  superintendence; 
yet,  however  active  they  may  be,  it  will  be  conceded  that  they  may 
fail  very  often  in  the  accomplishment  of  their  object.  We  may, 
doubtless,  by  a  minute  inspection  of  the  apparatus,  the  implements, 
and  the  supplies,  judge  if  the  light-keepers  have  at  their  command 
all  the  elements  requisite  to  an  efficient  service,  and  if  they  are  em- 
ployed with  all  proper  care.  We  may  equally  discover,  either  from 
observations  made  at  a  distance,  or  unexpected  visits,  if  the  pertur- 
bations observed  in  the  illumination  of  the  light-houses  arise  from 
the  negligence  of  the  keepers,  or  from  their  want  of  capacity  ;  but 
these  means  only  afford  us  an  idea  of  the  mean  state  of  the  illumin- 
ation, and  from  which  we  may  accidentally  discover  some  isolated 
facts  ;  but  that  will  not  suffice  for  the  proper  direction  of  a  service 
of  public  safety,  the  normal  condition  of  which  should  never  be  per- 
mitted to  be  interrupted. 

To  obtain  a  more  positive  and  a  more  efficient  control,  without  re- 
course to  an  unremitted  supervision,  which  would  require  a  large 
number  of  special  agents,  it  has  appeared  to  me  that  the  most  direct 
and  the  surest  means  was  to  require  the  principal  light-house  keep- 


181 

ers  to  keep  a  regular  account  of  the  oil  consumed  each  night  for  the 
illumination  of  their  lights.  Doubtless  there  is  reason  to  fear  that 
these  accounts  will  not  always  be  correct ;  but  we  shall,  sooner  or 
later,  detect  false  declarations  by  tne  details  of  the  monthly  tables, 
of  which  we  will  speak  hereafter. 

This  new  plan,  already  put  into  practical  operation  with  perfect 
success  in  some  light-houses,  is  only  applicable  to  the  lenticular  ap- 
paratus, illuminated  by  lamps  with  multiple  wicks.  These  lamps  re- 
quire in  their  management  unremitted  attention  and  care,  to  insure 
a  proper  development  of  their  flames.  We  have,  also,  generally  to 
encounter  the  lazy  tendency  of  the  keepers  in  keeping  habitually 
the  flames  of  the  lamps  below  their  normal  height. 

This  is  a  capital  point,  and  is  the  hinge  on  which  the  whole  light- 
house service  turns. 

The  table  to  be  filled  by  the  principal  keepers  must  be  kept  in 
conformity  to  the  accompanying  model,  (A1)  divided  into  six  columns, 
which  comprise  respectively  the  following  indications  : 

First  column,  the  day  of  the  month. 

Second  column,  the  hour  of  lighting. 

Third  column,  the  hour  of  extinguishing. 

Fourth  column,  the  duration  of  the  illumination. 

Fifth  column,  the  weight  of  the  oil  consumed. 

Sixth  column,  the  remarks. 

The  direct  weight  of  the  oil  put  each  day  into  the  reservoir  of  the 
lamp,  and  the  residue  which  is  drawn  off  after  extinguishing  the 
light,  will  present  in  the  service  a  complication  which  may  be 
avoided  by  means  of  a  gauging  table. 

To  construct  that  table  we  may  proceed  as  follows  :  Refill  the  res- 
ervoir of  the  lamp  by  pouring  one  kilogramme  of  oil  at  a  time  into 
it ;  note  at  each  time  the  number  in  millimetres  corresponding  to 
the  depth  of  the  liquid,  and,  in  dividing  by  ten  the  successive  dif- 
ferences, we  will  determine  the  numbers  answering  to  the  graduated 
weight  of  each  hectogramme. 

If  the  three  or  four  lamps  employed  in  the  light-house  have  not 
their  reservoirs  of  exactly  the  same  shape,  it  will  become  necessary 
to  construct  a  special  gauging  table  for  each  lamp,  which  must,  in 
that  case,  be  distinctly  marked,  so  that  they  may  not  produce  mis- 
takes. The  reports  of  the  consumption  of  oil  for  each  month  must 
be  signed  (at  the  end  of  each  month)  by  the  principal  keepers,  who 
will  address  them  in  triplicate  to  the  deputy  of  the  lighting  contrac- 


182 

tor,  or  to  the  conductor  of  the  arrondissement,  according  as  the  sup- 
plies are  furnished  by  contract  or  the  administration.  One  of  the 
three  copies  will  be  retained  by  the  deputy  or  conductor,  and  the 
two  others,  with  the  signature  of  that  agent  upon  them,  must  be 
transmitted  to  the  engineer  of  the  arrondissement.  Lastly,  one  of 
the  two  last  must  be  sent  to  the  engineer-iii-chief,  who,  after  hav- 
ing signed  it  with  or  without  remarks,  addresses  it  to  the  secretary 
to  the  commission  of  lights. 

Independently  of  these  tables,  destined  specially  to  control  the 
nocturnal  service  of  the  lighting  establishment,  it  is  necessary  to 
continue  to  require  the  principal  keepers  of  the  lights  under  the  ad- 
ministration, as  well  as  those  under  the  contractors,  to  furnish 
monthly  statements  of  the  condition  of  those  supplies  the  most 
essential  to  the  illuminating  service. 

The  accompanying  model  (B2)  is  used  by  the  administration,  and 
is  applicable  to  the  contracts,  by  substituting  the  approval  of  the 
deputy  of  the  contractor  for  that  of  the  conductor  or  agent  of  the 
administration.  These  latter  reports  must  be  made  out  in  quadru- 
plicate, disposed  of  in  the  same  manner  that  the  others  were,  and 
forwarded  under  the  same  cover. 

This  second  precautionary  measure  will  have  the  advantage  of 
furnishing  a  base  of  verification  for  the  daily  consumption  of  oil,  and 
of  apprizing  the  engineers  at  the  same  time,  more  readily,  if  the 
light-houses  are  supplied  at  all  times  with  all  the  objects  necessary 
as  well  for  the  service  of  the  illumination  as  the  maintenance  of  the 
apparatus  confided  to  the  light- keepers. 

To  prevent  these  new  measures  from  imposing  any  expenses  upon 
the  contractors  not  contained  in  the  table  of  charges,  the  adminis- 
tration will  furnish  the  lithographed  sheets  necessary  for  the  keep- 
ing of  the  two  different  tables  ;  and  they  will  be  sent  under  cover  to 
the  engineers  or  conductors. 

I  pray  you,  sir,  to  have  the  kindness  to  communicate  this  circular 
to  the  engineers  and  conductors  charged,  under  your  orders,  with 
the  service  of  the  light-houses,  and  require  the  strictest  execution 
of  all  duties  embraced  in  it. 

Receive,  sir,  the  assurance  of  my  very  distinguished  consideration, 


Under  Secretary  of  State  for  the  Public  Works. 
To  Monsieur ,  Engineer -in-chief  at 


183 


[Translated  from  the  French.] 
MEMOIR  PRESENTED  TO  THE  ACADEMY  OF  SCIENCES,  JANUARY  8,  1844. 

(Letourncau  &  Cie. ,  successors  of  Messrs.  Soliel,  sr.,  and  Fra^ois,  jr.,  constructors  of 
dioptric  lights  upon  the  system  of  Mr.  A.  Fresnel,  "Rue  des  Poiggonnieres,  No.  24  pres 
et  hors  la  barriere  Poissonnieres  a  Paris."] 

Note  upon  tJie  catadioptric  apparatus  constructed  by  Mr.  Francois,  jr., 
for  the  Scotch  light  at  Skerry  uore. — (Commissaries,  MM.  Arago, 
Mathieu,  Babinet.) 

The  lenticular  apparatus  imagined  by  M.  Augustin  Fresnel  com- 
prises, independently  of  the  fixed  or  movable  dioptric  drum,  an  ac- 
cessory part,  destined  to  collect  and  direct  towards  the  horizon  the 
luminous  rays  which,  issuing  from  the  focal  centre,  pass  above  and 
below  the  lenses. 

This  accessory  part  has  been  in  most  cases  formed  by  a  system  of 
fixed  concave  mirrors,  arranged  in  horizontal  zones,  both  above  and 
below  the  lenticular  drums. 

In  the  two  light-houses  of  Cordouan  and  Marseilles,  the  revolving 
dioptric  drum  is  surmounted  by  a  system  equally  movable,  composed 
of  eight  lenticular  panels  arranged  in  the  form  of  a  truncated  pyra- 
mid, and  as  many  plane  mirrors  to  convey  towards  the  horizon  the 
eight  luminous  beams  of  light  emerging  perpendicularly  to  the  faces 
of  the  pyramid.  A  third  combination,  preferable  to  the  two  others 
in  the  double  aspect  of  theory  and  practice,  has  been  applied  by 
the  inventor  to  the  small  lenticular  lights  of  twenty-five  to  thirty 
centimetres  of  interior  diameter.  In  these  apparatus,  which,  in 
consequence  of  their  small  size,  are  not  adapted  to  the  employment 
of  mirrors,  the  accessory  catoptric  system  has  been  replaced  by  a 
catadioptric  system  of  rings  or  zones,  in  triangular  section,  produc- 
ing total  reflection. 

The  first  apparatus  of  this  description  Avas  constructed  a  short 
time  before  the  death  of  M.  Augustin  Fresnel,  by  M.  Tabouret, 
conductor  of  bridges  and  roads,  attached  to  the  special  service  of 
the  light-houses. 

The  application  of  this  system  to  the  apparatus  of  the  largest  size 
ought,  at  that  time,  to  have  appeared  almost  impossible.  Scarcely, 
•in  fact,  could  the  shape  of  the  dioptric  rings  of  seventy-five  to 
eighty  centimetres  in  diameter  for  the  large  plano-convex  lenses  be 
obtained.  As  to  the  fixed  dioptric  drums,  of  diameters  exceeding 


184 

thirty  centimetres,  they  were  composed  of  cylindrical  elements,  the 
assemblage  of  which  presented,  in  place  of  an  annular,  a  polygonal 
system  of  sixteen  sides  for  the  apparatus  of  fifty  centimetres  diam- 
eter, (third  order  smaller  model ; )  twenty  sides  for  the  apparatus  of 
one  metre  in  diameter,  (third  order  larger  model;)  twenty-four 
sides  for  the  apparatus  of  one  metre  forty  centimetres  in  diameter, 
(second  order  ; )  and  thirty-two  sides  for  the  apparatus  of  one  metre 
eighty-four  centimetres  in  diameter,  (first  order.) 

A  catadioptric  polygonal  system  could,  without  doubt,  be  exe- 
cuted by  the  means  employed  for  the  polygonal  dioptric  system  ; 
but  the  adjustment  of  such  a  multitude  of  prisms  of  reflection,  the 
positions  of  wrhich  could  not  be  exactly  regulated  except  when  put 
up,  presented  an  inadmissible  complication. 

It  was  necessary,  for  the  practical  solution  of  the  problem,  that 
the  moulding  and  cutting  of  the  large  pieces  of  glass  should  be  per- 
formed by  an  improved  method.  A  manufacturer  of  mirrors  at 
Newcastle-upon-Tyne,  England,  (Mr.  Cookson,)  placed,  with  regard 
to  the  making  experiments  upon  the  subject,  in  a  singularly  favor- 
able position,  because  of  the  facilities  of  every  description  which  his 
vast  establishment  afforded  him,  made  the  first  attempt,  in  1836,  to 
construct  the  dioptric  drums  of  the  first  order  entire,  which  up  to 
that  time  had  been  formed  in  prisms  of  thirty-two  panels.  The  re- 
sults of  these  first  essays,  without  being  fully  satisfactory,  stimula- 
ted the  zeal  of  the  French  artists,  who  were  devoting  themselves  to 
the  fabrication  of  the  lenticular  apparatus  ;  and  very  soon  after,  we 
obtained  dioptric  drums  of  nearly  two  metres  in  diameter,  executed 
entire,  with  a  precision  which  increased  the  useful  effect  of  that 
principal  part  of  the  apparatus  about  one-fourth. 

From  that  time  the  project  of  constructing  upon  a  large  scale  the 
catadioptric  apparatus  was  permitted  to  recommence,  with  some 
chances  of  srfccess.  However,  the  considerations  of  expense  and  little 
prospect  of  profits,  &c.,  were  very  discouraging. 

Nevertheless,  the  able  Scotch  engineer  charged  with  the  construc- 
tion of  the  Skerry vore  light-house  (Mr.  Alan  Stevenson)  devoted 
himself  with  zeal  and  assiduity  to  the  idea  of  crowning  that  monument 
(which  cost  about  two  millions  of  francs)  with  the  most  perfect  illumi- 
nating apparatus  which  it  was  possible  to  construct  in  the  present 
state  of  the  arts  and  sciences. 

The  programme  was  adopted  by  the  commission  of  Scotch  light- 
houses, and  it  was  determined  that  the  Skerryvore  rock  should  be 


185 

marked  by  a  catadioptric  apparatus  of  the  first  order,  the  optical  parts 
of  which  should  be  constructed  at  Paris. 

A  correspondence  followed  upon  the  subject  between  Mr.  Alan 
Stevenson  and  Mr.  Leonor  Fresnel,  the  engineer  secretary  of  the  com- 
mission of  French  lights.  The  latter  first  calculated  the  elements  of, 
and  caused  to  be  constructed,  as  a  first  attempt,  two  catadioptric  ap- 
paratus of  one  metre  diameter,  (third  order,)  one  of  which,  construct- 
ed at  the  establishment  of  Mr.  Henry  Lepaute,  has  illuminated  for 
some  months  past  the  entrance  to  the  port  of  Gravelines  ;  and  the 
other,  constructed  by  M.  Francois,  jr.,  is  destined  for  the  light-house 
which  is  being  erected  at  the  mouth  of  the  Abervrach,  upon  the 
northwest  coast  of  Finisterre. 

In  spite  of  the  complete  success  of  the  first  experiment,  the  fabri- 
cation of  the  reflecting  rings  of  the  first  order  always  presented  itself 
as  a  grave  and  perilous  enterprise. 

Even  the  secretary  to  the  commission  of  French  lights,  in  remitting 
to  M.  Francois,  jr.,  the  table  of  the  centres  and  radii  of  curvature  of 
the  nineteen  glass  rings  or  zones  which  were  required  to  form  the 
catadioptric  part  of  a  first  order  light,  deemed  it  his  duty  to  insist 
that  that  artist  should  weigh  well  the  engagement  which  he  was  about 
entering  into  with  the  administration  of  the  Scotch  lights.  M.  Fran- 
cois, jr.,  did  not  hesitate  a  moment.  He  undertook  resolutely  a  work 
of  great  public  utility,  which  required  in  its  accomplishment  the  over- 
coming of  grave  difficulties. 

One  may  form  some  idea  of  these  difficulties  by  a  simple  inspection 
of  the  table  of  radii  of  curvatures  of  the  reflecting  surfaces  of  the 
catadioptric  rings,  which  vary  from  6,816  metres  to  8,749  metres. 

The  ring  No.  1,  which  answers  to  the  maximum  radius,  has  two 
metres  of  exterior  diameter.  The  two  adjacent  sides  of  the  obtuse 
angle  (of  117°  26'  42")  have  respectively  92.380  millimetres,  and 
95.209  millimetres  of  length.  The  two  refracting  faces  have  been 
supposed  rectilinear  in  the  calculation  ;  but  in  consequence  of  the 
difficulty  of  executing  with  precision  conic  surfaces,  we  have  (follow- 
ing the  ingenious  idea  of  the  inventor)  substituted  for  the  two  gene- 
rating right  lines  two  arcs  of  a  circle  of  equal  radius,  (four  metres,) 
taking  care  to  turn  them  in  an  inverse  sense,  so  that  the  convergence 
resulting  from  the  convexity  of  one  face  was  compensated  by  the  di- 
vergence resulting  from  the  concavity  of  the  other  face. 

Each  ring  has  been  composed  of  four  equal  arcs. 


186 

These  pieces  were  first  run  into  a  rough  shape  at  the  manufactory 
of  Saint  Gobain,  in  the  moulds  furnished  by  M.  Francois,  jr. 

The  first  operation  presented  difficulties  which  would  have  dis- 
couraged one  less  determined,  and  one  possessing  a  mind  less  fertile 
in  resources. 

Each  rough  ring  was  afterwards  rubbed  with  grit  or  freestone* 
smoothed  with  emery,  and  polished  with  English  red,  upon  a  circle 
moved  by  steam  machinery. 

It  may  be  conceived  how  many  precautions  are  required  in  the 
perfect  execution  of  an  annular  reflecting  surface,  which  is  cut  or 
shaped  by  means  of  a  rubber,  grinding  it  with  an  oscillating  arm  or 
lever  of  eight  metres  seventy-five  centimetres  in  length,  and  how 
much  more  care  ought  to  be  taken  to  study  the  means  by  which  to 
insure  the  rigidity  of  this  arm  or  lever,  as  well  as  the  exactitude  of 
the  position  and  the  fixedness  of  the  centre  of  rotation. 

Not  only  has  this  difficult  problem  been  solved  with  perfect  success, 
but  it  has  been  done  Avithout  groping  or  wavering,  without  false 
movements,  and  Avithout  having  to  regret  the  loss  of  one  ring  broken 
upon  the  grinding  circular  frame. 

After  having  been  verified  by  the  reflection  of  a  red  ball  placed  in 
their  focus,  the  rings  or  zones  \vere  put  together  in  panels. 

To  fulfil  the  requirements  of  Mr.  Alan  Stevenson,  M.  Francois,  jr., 
divided  his  catadioptric  dome  or  cupola  into  eight  spindles,  embracing, 
each,  forty-five  degrees.  One  of  these  spindles  has  been  put  under 
experiment  tAvice  at  the  observatory.  Illuminated  by  a  lamp  of  the 
first  order,  Avith  four  concentric  Avicks,  burning  from  670  to  700 
grammes  of  oil  per  hour,  this  catadioptric  panel  presented  a  brilliant 
bar  of  light,  Avhich,  after  the  mean  of  six  observations  of  equal  shadows, 
Avas  equivalent  to  one  hundred  and  forty  burners  of  the  Carcel  lamp, 
burning  forty-tAvo  grammes  of  oil  her  hour. 

The  catoptric  cupola,  Avhich  theneAv  system  replaces,  is  composed, 
ordinarily,  of  seven  horizontal  zones,  containing  each  thirty-two  con- 
cave mirrors.  Its  brilliancy  appeared  greater  or  lesser  according  as 
it  Avas  placed  in  the  direction  of  the  axis,  or  of  the  intervals  of  the 
mirrors,  but  the  mean  lustre  corresponding  to  the  useful  effect  has 
been  found  to  be  eighty-seven  burners  of  Carcel. 

Thus,  then,  the  useful  effect  of  the  HCAV  crown  is  to  that  of  the  old 
one  as  1.61  to  1. 

It  is  to  be  presumed  that  the  same  results  Avould  be  found  to  exist, 
or  pretty  nearly  the  same,  for  the  part  below  the  lenticular  drum  ; 


187 

and  as  we  have  found  forty-six  burners  for  the  mean  brilliancy  of  the 
four  lower  zones  of  mirrors,  we  may  count  upon  seventy-four  burners 
for  the  brilliancy  of  the  six  corresponding  catadioptric  rings.  The 
value  of  a  fixed  lenticular  drum  of  the  first  order,  with  annular  ele- 
ments, being,  besides  equal  to  300  burners,  Ave  may  recapitulate  by 
the  following  little  table  the  approximation  to  which  it  refers  : 

Lustres  or  brilliancy,  measured  in  burners  of  Cared. 

First  system.          Second  system. 
1.   Fixed  dioptric  drum 360  burners.      360  burners. 

" 


Total 493       ;'  574 

Finally,  the  substitution  of  the  prismatic  rings  in  place  of  the 
mirrors  of  a  first  order  fixed  light,  will  augment  the  mean  brilliancy 
eighty-one  burners — that  is  to  say,  more  than  equal  to  the  value  of  a 
light  of  the  third  class. 

To  that  increase  of  the  effect  of  sixteen  and  a  half  per  cent,  upon 
the  total  brilliancy,  two  capital  advantages  are  joined  :  one,  the  equal 
distribution  of  light,  and  the  other  the  stability  of  the  reflecting 
power  of  the  catadioptric  rings. 

Although  the  fiscal  question  is  only  one  of  a  secondary  consideration 
here,  yet  perhaps  it  may  not  be  superfluous  to  say  a  word  upon  it  in 
concluding. 

The  system  of  eleven  zones  of  curved  mirrors  of  a  light 

of  the  first  order  costs,  including  the  subsidiary  pieces,  6, 00.0  francs. 

The  corresponding  catadioptric  system  has  been  ten- 
dered for  the  price  of 20, 000  " 

Augmentation    14, 000        " 


If,  then,  we  take  for  example  a  light  of  the  first  order, 
costing  annually  for  illuminating,  and  the  ordinary 
service  7, 500 

Add  the  interest  on  first  cost  of  illuminating  apparatus  1,500 


9,000 

we  will  find  that  the  above  calculated  advantage  of  sixteen  and  a  half 
per  cent,  would  be  equal  to  1.485  francs,  a  larger  sum  than  the  in- 
terest upon  the  14,000  francs,  the  excess  of  the  price  of  acquisition. 


188 

Thus,  then,  considering  the  new  system  in  a  fiscal  point  of  view 
only,  we  perceive  that  the  augmentation  of  useful  effect  which  it  will 
produce  will  not  be  acquired  at  too  high  a  price. 


Mitchell's  screw-piles  and  moorings. 

SIRS  :  Permit  us  to  present  to  your  notice  a  brief  description  of 
our  patent  mooring,  an  instrument  now  well  known  in  many  of  the 
principal  ports  and  harbors  of  the  United  Kingdom,  where  they  have 
been  for  a  considerable  time  in  constant  use,  and  where  we  may  add, 
they  have  had  the  unqualified  approbation  of  every  scientific  and 
nautical  person  who  has  had  occasion  to  consider  the  subject. 

The  mooring  is  constructed  (as  its  name  implies)  on  the  principle 
of  the  screw,  but  differing  essentially  in  form  from  that  well  known 
instrument ;  for  while  the  spiral  thread  makes  little  more  than  one 
turn  round  its  shaft,  it  is,  at  the  same  time,  extended  to  a  very  broad 
flange,  the  hold  which  it  takes  of  the  ground  being  proportional  with 
its  breadth  of  disk. 

Where  it  is  necessary  to  provide  against  a  very  heavy  strain,  we 
have  hitherto  used  moorings  of  three  feet  six  inches  diameter,  and  the 
principle  is  capable  of  still  further  extension. 

A  mooring  of  the  above  diameter  presents  a  resisting  surface  equal 
to  about  ten  square  feet,  whereas  the  palm  of  the  largest  anchor  in 
the  British  navy  does  not  exceed  half  that  size  ;  and  some  estimate 
of  its  holding  power  may  be  formed,  when  it  is  shown  that  this  broad 
surface  can  be  screwed  to  a  depth  many  times  greater  than  that  to 
which  the  palm  of  an  anchor  can  ever  descend. 

The  method  of  laying  down  this  mooring  is  briefly  thus  : 

A  strong  mooring  chain  being  so  attached  to  it  as  to  allow  the  screw 
to  turn  freely  without  carrying  the  chain  round  with  it,  a  powerful 
iron  shaft  is  then  fixed  firmly  on  the  upper  part  of  the  mooring,  which 
is  formed  square  for  that  purpose,  fitting  in  the  same  manner  as  a  key 
to  a  watch  in  winding  it  up  :  it  is  then  lowered  by  the  mooring  chain, 
joint  after  joint  being  added  to  the  shaft  till  the  mooring  has  reached 
the  ground.  Eight  levers  of  twelve  feet  in  length  are  then  applied 
to  the  shaft,  in  the  manner  of  a  capstan,  when  the  operation  of  screw- 
ing the  mooring  into  the  ground  commences. 

Two  boats  or  barges  having  been  moored  firmly,  head  and  stern, 
close  alongside  each  other,  and  the  upright  shaft  rising  between  them 


189 

about  midships,  the  men  place  themselves  at  the  bars  or  levers,  and 
move  round  from  one  boat  to  the  other,  the  two  giving  them  a  safe 
and  convenient  platform.  By  a  simple  contrivance,  the  levers  are 
occasionally  shifted  upwards,  as  the  screw  and  the  shaft  sink  into  the 
ground. 

When  the  number  of  men  employed  can  no  longer  force  the  screw 
round,  the  levers  are  removed  and  the  shaft  drawn  out  of  the  ground, 
leaving  the  mooring  firmly  embedded,  with  the  chain  attached  to  it; 
a  buoy  being  shackled  to  the  other  end  of  the  chain,  the  work  is 
completed;  the  time  required  for  the  whole  operation  seldom  exceed- 
ing a  few  hours. 

These  moorings  have  been  placed  in  every  description  of  ground — 
rock  not  excepted;  and  the  qualities  which  entitle  them  to  the  patron- 
age of  the  public  are,  perfect  security  to  shipping,  great  economy, 
and  an  entire  freedom  from  the  many  objections  to  which  other  moor- 
ings are  liable.  On  these  subjects,  however,  we  shall  not  enlarge, 
but  refer  to  the  letters  and  testimonials  hereto  annexed,  which  have 
been  selected  from  a  great  number  of  documents  received  on  the 
subject. 

Any  communications  addressed  to  Alexander  Mitchell  &  Son,  engi- 
neers, 2  Alfred  street,  Belfast,  shall  receive  prompt  attention. 

We  have  the  honor  to  be,  sirs,  your  very  obedient  servants. 

ALEXANDER  MITCHELL  &  SON. 

Lieuts.  JENKINS  and  BACHE,  U.  S.  N. 


Extract  from  the  report  of  Captain  Canfield,  Corps  of  Topographical 
Engineers,  to  Colonel  Abert,  dated  October  1,  1851,  and  printed  as 
part  of  Senate  document  No.  1,  of  the  session  1851 -'52. 

As  there  is  only  one  burner  or  lamp  in  this  apparatus,  it  is  evident 
that  any  accident  by  which  the  lamp  was  put  out  would  leave  them 
in  total  darkness;  differing  essentially  in  this  respect  from  the  com- 
mon reflecting  lights,  where,  if  several  lamps  go  out,  there  will  still 
be  a  light  of  some  kind.  To  make  it  certain  that  the  lamp  is  kept 
burning,  it  is  usual  to  keep  a  watchman  constantly  with  the  light. 

As  a  substitute  for  the  watchman,  and  that  the  keeper  may  know 
immediately  of  any  accident  of  this  kind,  I  have  fixed  a  contrivance 
at  Waugoshance,  by  which  the  the  fog-bell  will  commence  ringing  as 
soon  as  the  light  is  put  out. 


190 

This  is  effected  by  making  use  of  the  expanding  and  contracting 
power  of  a  copper  tube,  when  heated  and  cooled.  The  tube  is  made 
to  form  a  part  of  the  chimney  of  the  lamp. 

The  amount  of  the  expansion  under  this  heat  is  very  small,  (about 
one-twentieth  of  an  inch.)  But  the  expansive  force  being  very 
great,  I  use  a  lever,  with  a  short  fulcrum  running  from  the  lamp  at 
the  centre  to  the  side  of  the  lantern,  and  increase  the  amount  of  the 
movement  here  ten  times.  To  the  end  of  this  lever  is  attached  a 
copper  wire,  which  wire  is  also  attached  to  another  lever  on  the  floor 
of  the  bell  machine,  forty  feet  below  the  lantern. 

The  movement  by  this  second  lever  is  again  increased  six  times; 
so  that  the  motion  here  amounts  to  full  three  inches. 

This  last  lever,  when  the  copper  tube  is  heated  by  the  lamp,  is  in 
a  position  to  hold  an  iron  hook,  so  that  the  hook  will  catch  one  of  the 
spurs  of  the  wheel  which  moves  the  clapper-shaft. 

The  catching  of  the  spur,  of  course,  stops  the  machine;  when  the 
light  goes  out,  the  copper  tube  of  the  chimney  cools  and  contracts. 
The  lever  at  the  machine  is  raised,  and  the  hook  by  its  own  weight 
swings  clear  of  the  spur  of  the  wheel,  and  the  machine  moves  on, 
and  the  bell  rings;  and  unless  it  is  stopped,  continues  to  ring  until 
the  machine  runs  down. 

This  arrangement  is  found  to  answer  perfectly,  and  is  tested  every 
morning  when  the  light  is  put  out. 


EXTRACTS  FROM  TREATISES  ON  LIGHT-HOUSE    ILLUMINATIONS,    &C.,    &C.,    AC. 

Extracts  from  Mr.  Alan  Stevenson's  Treatise  on  Light-houses,  d'c. 

[John  Wrale,  London,  1850.  ] 

Colza  oil  has  been  introduced  in  England  into  all  the  lights,  whether 
catoptric  or  dioptric;  but  in  Scotland  its  general  use  has  as  yet  been 
confined  to  the  dioptric  lights,  and  such  catoptric  lights  as  revolve, 
and  are  not  likely  to  be  changed  to  the  dioptric  system.  In  the 
catoptric  lights,  the  only  reason  for  not  making  an  equally  extensive 
trial  is  the  necessity  for  renewing  all  the  burners,  which  require  to 
be  so  constructed  as  to  receive  thick  wicks  of  brown  cotton;  and  it 
has,  until  lately,  been  considered  prudent  to  proceed  with  some  cau- 
in  changing  the  apparatus,  so  as  to  suit  it  for  burning  a  patent  oil, 
the  circumstances  attending  the  regular  and  extensive  supply  and 


191 

the  price  of  which,  can  hardly  yet  be  fully  known.  The  change  is 
proceeding  gradually  from  the  use  of  spermaceti  to  that  of  the  colza 
oil;  arid,  in  a  few  seasons,  the  whole  will  be  completed,  as  nearly  all 
the  revolving  catoptric  lights  have  been  altered;  and  the  change  on 
the  fixed  lights  has  been  only  delayed  until  they  shall  be  converted 
to  the  dioptric  system,  so  that  one  change  may  serve  every  purpose 
at  once.  *  ****** 

Great  as  Argand's  improvement  undoubtedly  was,  the  value  of  the 
lamp  alone  as  a  means  for  the  illumination  of  light-houses  must  be 
regarded  as  comparatively  small.  The  primary  object  of  a  light-house 
is  to  give  early  notice  to  the  mariner  of  his  approach  to  the  coast; 
and  it  is  therefore  necessary  that  the  light  be  of  such  a  kind  that  it 
may  be  seen  at  a  great  distance.  Every  one  is  practically  acquainted 
with  the  fact  that  the  rays  proceed  in  all  directions  from  a  luminous 
body  in  straight  lines;  and  if  we  could  obtain  a  ball  equally  luminous 
in  every  part  of  its  surface,  it  would  give  an  equal  share  of  light  to 
every  part  of  the  inner  surface  of  a  hollow  sphere,  whose  centre 
shall  coincide  with  the  centre  of  the  ball.  Again,  if  an  opaque  body 
were  placed  between  the  luminous  ball  and  the  hollow  sphere,  the 
part  opposite  that  body  would  be  deprived  of  the  light  by  the  inter- 
ception of  the  rays,  and  no  light  would  emerge  from  a  hole  bored  in 
that  part  of  the  surface  of  the  hollow  sphere.  The  bearing  of  these 
facts  is  obvious;  and  no  one  can  fail  to  perceive  that  in  the  case  of  a 
light-house  illuminated  by  a  single  unassisted  burner,  a  seaman  could 
only  receive  the  benefit  of  that  small  portion  of  light  which  emerges 
from  the  lamp  in  a  line  joining  his  eye  and  the  centre  of  the  flame. 
The  other  rays  would  be  occupied  partly,  but  in  a  very  small  propor- 
tion, in  making  the  light  visible  in  other  parts  of  the  horizon;  while 
all  the  rest  would  be  lost  by  escaping  upwards  into  the  sky,  or  down- 
wards below  the  plane  in  which  seamen  can  see  a  light-house.  This 
state  of  matters  would  be  little  improved  by  increasing  the  number 
of  burners,  as  the  effective  part  of  the  light  would  only  be  augmented 
by  the  addition  of  an  equally  trifling  portion  of  light  from  each  burner. 
The  small  pencils  of  rays  thus  meeting  at  the  eye  of  a  distant 
observer,  would  form  a  very  minute  fraction  of  the  whole  quantity  of 
light  uselessly  escaping  above  and  below  the  horizon,  and  also  at  the 
back  of  each  flame;  and  the  wasteful  expenditure  of  light  would  be 
enormous.  By  such  a  method,  no  practically  efficient  sea-light  could 
ever  have  been  obtained.  * 

The   best  proportions  for  paraboloi'dal  mirrors  depend  on  the  ob- 


192 

jects  which  they  are  meant  to  attain.  Those  which  are  intended  to  give 
great  divergence  to  the  resultant  beams,  as  in  fixed  lights,  capable 
of  illuminating  the  whole  horizon  at  one  time,  should  have  a  short 
focal  distance;  while  those  mirrors  which  are  designed  to  produce  a 
nearer  approach  to  parallelism  (as  in  the  case  of  revolving  lights, 
which  illuminate  but  a  few  degrees  of  the  horizon  at  any  one  instant 
of  time)  will  have  the  opposite  form.  Those  two  objects  may,  no 
doubt,  be  attained  with  the  same  mirror,  by  increasing  or  diminish- 
ing the  size  of  the  burner;  but  that  is  by  no  means  desirable,  as  any 
change  in  the  size  of  a  burner,  which  is  found  to  be  the  best  in  other 
respects,  must  be  considered  as  to  some  extent  disadvantageous. 
*  *  %  #  *  *  * 

The  large  mirrors  used  in  the  Northern  light-houses  have  about 
twelve-seventeenths  of  the  whole  light  of  the  lamp  incident  on  their 
surface;  the  rest  escapes  in  the  comparatively  useless  state  of  natu- 
rally radiating  light.  Several  arrangements  have  been  proposed  for 
economising  this  light,  which  will  be  afterwards  noticed. 

The  reflectors  used  in  the  best  light-houses  are  made  of  sheet- 
copper,  plated  in  the  proportion  of  six  ounces  of  silver  to  sixteen 
ounces  of  copper.  They  are  moulded  to  the  parabaloi'dal  form  by  a 
delicate  and  laborious  pro.cess  of  beating  with  mallets  and  hammers 
of  various  forms  and  materials,  and  are  frequently  tested  during  the 
operation  by  the  application  of  a  mould  carefully  formed.  After 
being  brought  to  the  curve,  they  are  stiffened  round  the  edge  by 
means  of  a  strong  bizzle,  and  a  strap  of  brass  which  is  attached  to  it 
for  the  purpose  of  preventing  any  accidental  alteration  of  the  figure 
of  the  reflector.  Polishing  powders  are  then  applied,  and  the  in- 
strument receives  its  last  finish. 

In  light-houses  of  moderate  height,  the  proper  position  for  the  re- 
flector itself  is  perfect  horizontality  of  its  axis,  which  may  be  ascer- 
tained with  sufficient  accuracy  by  trying  with  a  plummet  whether 
the  lips  of  the  instrument,  which  we  may  conclude  to  be  at  right 
angles  to  the  plane  of  its  axis,  be  truly  vertical.  In  light-rooms 
very  much  elevated  above  the  sea,  however,  the  dip  of  the  horizon 
becomes  notable;  and  a  slight  inclination  forwards  should  be  given 
to  the  face  of  the  reflectors,  so  that  their  axes  produced  may  be 
tangents  to  the  earth  at  the  visible  horizon  of  the  light-room;  an 
arrangement  which,  in  practice,  may  be  easily  made  by  reflecting 
the  sea  horizon  in  a  small  mirror  placed  at  the  focus,  and  inclined  at 
45°  to  the  axis  of  the  paraboloid,  so  that  the  image  of  the  sea-line 


193 

may  reach  the  eye  in  the  line  of  the  parameter  in  the  same  manner, 
as  is  afterwards  noticed  in  speaking  of  the  inclination  of  the  curved 
mirrors  used  in  addition  to  the  refractors  in  certain  dioptric  fixed 
lights.  This  dip  of  the  reflector,  however,  must  not  be  permitted 
to  interfere  with  the  perfect  horizontality  of  the  top  of  the  burner, 
which  is  indispensable  to  its  proper  burning. 

******** 

The  effect  of  an  annular  lens,  in  combination  with  the  great  lamp, 
may  be  estimated  at  moderate  distances  to  be  nearly  equal  to  that  of 
between  3,000  and  4,000  Argand  flames  of  about  an  inch  diameter; 
that  of  a  cylindric  refractor  at  about  250;  and  that  of  a  curved  mir- 
ror may  perhaps  on  an  average  be  assumed  at  about  10  Argand 
flames. 

The  dioptric  lights  used  in  France  are  divided  into  six  orders,  in 
relation  to  their  power  and  range ;  but  in  regard  to  their  character- 
istic appearances,  this  division  does  not  apply,  as,  in  each  of  the 
orders,  lights  of  identically  the  same  character  may  be  found,  differ- 
ing only  in  the  distance  at  which  they  can  be  seen,  and  in  the 
expense  of  their  maintenance.  The  six  orders  may  be  briefly 
described  as  follows  : 

1.  Lights  of  the  first  order  having  an  interior  radius  or  focal  dis- 
tance of  36.22  inches  (92oin-),  and  lighted  by  a  lamp  of  four  concentric 
wicks,  consuming  five  hundred  and  seventy  gallons  of  oil  per  annum. 

2.  Lights  of  the  second  order,  having  an  interior  radius  of  27.55 
inches  (70om>),  lighted  by  a  lamp  of  three  concentric  wicks,  consum- 
ing three  hundred  and  eighty-four  gallons  of  oil  per  annum. 

3.  Lights  of  the  third  order,  lighted  by  a  lamp  of  two  concentric 
wicks,  consuming  one  hundred  and  eighty-three  gallons  of  oil  por 
annum,  and  having  a  focal  distance  of  19.68  inches  (50cm-) 

4.  Lights  of  the  fourth  order,  or  harbor-lights,  having  an  internal 
radius  of  9.84  inches  (25cm<),  and  a  lamp  of  two  concentric  wicks, 
consuming  about  one  hundred  and  thirty  gallons  of  oil  per  annum. 

5.  Lights  of  the  fifth  order,  having  a  focal  distance  of  7.28  inches 
(18.5cm-);  and 

6.  Lights  of  the  sixth  order,  having  an  internal  radius  of  5.9  inches 
(15om'),  and  lighted  by  a  lamp  of  one  wick,  or  Argand  burner,  con- 
suming forty-eight  gallons  of  oil  per  annum,     The  more  minute  sub- 
divisions of  orders  I  consider  to  be  unnecessary. 

13 


194 

Those  orders  are  not  intended  as  distinctions,  but  are  character- 
istic of  the  power  and  range  of  lights,  which  render  them  suitable 
for  different  localities  on  the  coast,  according  to  the  distance  at 
which  they  can  be  seen.  This  division,  therefore,  is  analogous  to 
that  which  separates  our  lights  into  sea  lights,  secondary  lights,  and 
harbor  lights,  terms  which  are  used  to  designate  the  power  and 
position,  and  not  the  appearance  of  the  lights  to  which  they  are 
applied. 

Each  of  the  above  orders  is  susceptible  of  certain  combinations, 
which  produce  various  appearances,  and  constitute  the  distinctions 
used  for  dioptric  lights;  but  the  following  are  those  which  have  been 
actually  employed  as  the  most  useful  in  practice  : 

The  first  order  contains,  first,  lights  producing,  once  in  every 
minute,  a  great  flash,  preceded  by  a  smaller  one,  by  the  revolution 
of  eight  great  lenses  and  eight  smaller  ones  combined  with  eight 
mirrors;  second,  lights  flashing  once  in  every  half  minute,  and  com- 
posed of  sixteen  half  lenses.  Those  lights  may  have  the  subsidiary 
parts  simply  catoptric,  or  diacatoptric  :  and,  third,  fixed  lights, 
composed  of  a  combination  of  cylindric  pieces,  with  curved  mirrors 
or  catadioptric  zones  ranged  in  tiers  above  and  below  them. 

The  second  order  comprises  revolving  lights  with  sixteen  or  twelve 
lenses,  which  make  flashes  every  half  minute;  and  fixed  lights  varied 
by  flashes  once  in  every  four  minutes — an  effect  which,  as  already 
noticed,  is  produced  by  the  revolution  of  exterior  cylindric  pieces. 

The  third  order  contains  common  fixed  lights,  and  fixed  lights 
varied  by  flashes  once  in  every  four  minutes. 

The  fourth  order  contains  simple  fixed  lights,  and  fixed  lights  varied 
by  flashes  once  in  three  minutes. 

The  fifth  order  has  fixed  lights  varied  by  flashes  once  in  every 
three  minutes,  and  fixed  lights  of  the  common  kind.  It  has  been 
thought  necessary  to  change  the  term  "fixed  lights  varied  by 
flashes"  for  "fixed  lights  with  short  eclipses,"  because  it  has  been 
found  that  at  certain  distances  a  momentary  eclipse  precedes  the 
flash.  The  sixth  order  has  only  fixed  lights. 

These  distinctions  depend  upon  the  periods  of  revolution  rather 
than  upon  the  characteristic  appearance  of  the  light ;  and  therefore 
seem  less  calculated  to  strike  the  eye  of  a  seaman  than  those  em- 
ployed on  the  coasts  of  Great  Britain  and  Ireland.  In  conformity 


195 

with  this  system,  and  in  consideration  of  the  great  loss  of  light 
which  results  from  the  application  of  colored  media,  distinctions 
based  upon  color  have  been  generally  discarded  in  the  French  lights. 

The  distinctions  are  in  fact  only  four  in  number,  viz  :  fixed  ; 
fixed,  varied  by  flashes  ;*  revolving,  with  flashes  once  a  minute  ;  and 
revolving  with  flashes  every  half  minute.  To  those  might  be  added, 
revolving,  with  bright  periods  once  in  two  minutes,  and  perhaps 
flashing  once  in  Jive  seconds,  ( as  introduced  by  me  at  the  Little  Ross, 
but  I  cannot  say  with  such  complete  success  as  would  induce  me  to 
recommend  its  general  adoption.)  My  own  experience  would  also 
lead  me  to  reject  the  distinction  called  "fixed,  varied  by  flashes," 
which  I  do  not  consider  as  possessing  a  marked  or  efficient  character. 

Having  thus  fully  described  the  nature  of  the  catoptric  and  dioptric 
modes  of  illuminating  light-houses,  I  shall  conclude  with  a  com- 
parative view  of  the  merits  of  both  systems,  deduced  from  the 
experiments  made  at  Gullan-hill  during  the  winters  of  1832  and  1833, 
under  the  inspection  of  the  commissioners  of  Northern  lights.  The 
chief  practical  result  of  those  trials  was,  that  the  light  of  one  of  the 
great  annular  lenses  used  in  the  revolving  lights  of  the  first  order, 
was  equal  to  the  united  effect  of  eight  of  the  large  reflectors  em- 
ployed in  the  revolving  lights  on  the  Scotch  coast.  It  may  be  said, 
however,  that  the  diacatoptrict  combination  of  pyramidal  lenses 
and  plane  mirrors  of  Cordouan,  adds  the  power  of  more  than  two 
reflectors  to  the  effect  of  the  great  lens  ;  but  it  ought  to  be  re- 
membered that  in  the  French  lights  this  additional  power  is  used 
only  to  compensate  for  one  of  the  defects  of  the  system  by  lengthen- 
ing the  duration  of  the  flash,  and  therefore  contributes,  if  at  all, 
only  in  a  very  indirect  manner  to  render  the  light  visible  to  the 
mariner  at  a  greater  distance.  M.  Fresnel  found  that  from  the  smaller 
divergence  of  the  lens  the  eclipses  were  too  long  and  the  bright 
periods  of  the  revolution  too  short,  and  he  therefore  determined  to 
adopt  the  horizontal  deviation  of  7°  for  the  upper  lenses,  with  a  view 
to  remedy  this  defect.  Assuming,  therefore,  that  it  were  required  to 
increase  the  number  of  reflectors  in  a  revolving  light  of  three  sides, 
so  as  to  render  it  equal  in  power  to  a  dioptric  revolving  light  of  the 
first  order,  it  would  be  necessary  to  place  eight  reflectors  on  each 
face,  so  that  the  greatest  number  of  reflectors  required  for  this 

a  The  "  Feu  fixe,  varie  par  des  eclats,"  or  "Feu  fixe,  a  courtes  eclipses,"  of  Fresnel. 
f  I  use  this  word  to  designate  the  arrangement  of  pyramidal  lenses  and  plane  mirrors, 
by  which  the  light  is  first  refracted  and  then  Ttfleded. 


196 

purpose  may  be  taken  at  twenty-four.  M.  Fresnel  has  stated  the 
expenditure  of  oil  in  the  lamp  of  four  concentric  wicks  at  seven 
hundred  and  fifty  grammes  of  colza  oil  per  hour  ;  and  it  is  found  by 
experience  at  the  Isle  of  May  and  Inchkeith  that  the  quantity  of 
spermaceti  oil  consumed  by  the  great  lamp  is  equal  to  that  burned 
by  from  fourteen  to  sixteen  of  the  Argand  lamps  used  in  the  Scotch 
lights.  It  therefore  follows  that  by  dioptric  means  the  consumption 
of  oil  necessary  for  between  fourteen  and  sixteen  reflectors  will 
produce  a  light  as  powerful  as  that  which  would  require  the  oil  of 
twenty- four  reflectors  in  the  catoptric  system  of  Scotland ;  and 
consequently  that  there  is  an  excess  of  oil  equal  to  that  consumed 
by  ten  reflectors,  or  four  hundred  gallons  in  the  year,  against  the 
Scotch  system.  But  in  order  fully  to  compare  the  economy  of  pro- 
ducing two  revolving  lights  of  equal  power  by  those  two  methods,  it 
will  be  necessary  to  take  into  the  calculation  the  interest  of  the  first 
outlay  in  establishing  them. 

The  expense  of  fitting  up  a  revolving  light  with  twenty-four  re- 
flectors, ranged  on  three  faces,  may  be  estimated  at  £1,298,  and  the 
annual  maintenance,  including  the  interest  of  the  first  c  st  of  the 
apparatus,  may  be  calculated  at  £418  8s.  4c£.  The  fitting  up  a 
revolving  light  with  eight  lenses  and  the  diacatoptric  accessory 
apparatus,  may  be  estimated  at  £1,459,  and  the  annul  maintenance 
at  £354  10s.  4d.  It  therefore  follows  that  to  establish  and  after- 
wards maintain  a  catoptric  light  of  the  kind  called  revolving  ivhite, 
with  a  frame  of  three  faces,  each  equal  in  power  to  a  face  of  the 
dioptric  light  of  Cordouan,  an  annual  outlay  of  £63  18s.  more  would 
be  required  for  the  reflecting  light  than  for  the  lens  light;  while  for 
a  light  of  the  kind  called  revolving  red  and  white,  whose  frame  has 
four  faces,  at  least  thirty-six  reflectors  would  be  required  in  order 
to  make  the  light  even  approcah  an  equality  to  that  of  Cordouan  ;  and 
the  catoptric  light  would  in  that  case  cost  £225  more  than  the 
dioptric  light. 

The  effect  produced  by  burning  an  equal  quantity  of  oil  in 
revolving  lights  on  either  system  may  be  estimated  as  follows  :  In 
a  revolving  light  like  that  of  Skerryvore,  having  eight  sides,  each 
lighting  with  its  greatest  power  a  horizontal  sector  of  4°,  we  have 
32°  (or  units)  of  the  horizon  illuminated  with  the  full  power  of  three 
thousand  two  hundred  Argand  flames,  and  consequently  an  aggre- 
gate effect  of  one  hundred  and  two  thousand  four  hundred  flames, 
produced  by  burning  the  oil  required  for  sixteen  reflectors ;  while  in 


197 

a  catoptric  apparatus,  like  that  of  the  old  light  at  Inchkeith,  having 
seven  sides  of  one  reflector,  each  lighting  with  its  greatest  power  a 
sector  of  4°  25',  we  have  nearly  31°  (or  units)  of  the  horizon 
illuminated  with  the  full  power  of  four  hundred  Argand  flames, 
and  consequently  an  aggregate  effect  of  twelve  thousand  four  hun- 
dred flames  as  the  result  of  burning  the  oil  required  for  seven  re- 
flectors. Hence  the  effect  of  burning  the  same  quantity  of  oil  in 
revolving  lights  on  either  system  will  be  represented  respectively 

"by  —.   12,400  =  28,343  for  the  catoptric,  contrasted  with  102,400  for 

the  dioptric  light;  or,  in  other  words,  revolving  lights  on  the 
dioptric  principle  use  the  oil  more  economically  than  those  on  the 
catoptric  plan,  nearly  in  the  ratio  of  3.6  to  1. 

Let  us  now  speak  of  fixed  lights,  to  which  the  dioptric  method  is 
peculiarly  Avell  adapted.  The  effect  produced  by  the  consumption  of 
a  gallon  of  oil  in  a  fixed  light,  with  twenty-six  reflectors,  which  is 
the  smallest  number  that  can  be  properly  employed,  may  be  esti- 
mated as  follows :  The  mean  effect  of  the  light  spread  over  the 
horizontal  sector,  subtended  by  one  reflector,  as  deduced  from 
measurements  made  at  each  horizontal  degree,  by  the  method  of 
shadows,  is  equal  to  174  unassisted  Argand  burners.  If,  then,  this 
quantity  be  muliplied  by  360  degrees,  we  shall  obtain  an  aggregate 
effect  of  62,640,  which,  divided  by  1,040,  (the  number  of  gallons 
burned  during  a  year  in  twenty-six  reflectors,)  would  give  sixty 
Argand  flames  for  the  effect  of  the  light  maintained  throughout  the 
year  by  the  combustion  of  a  gallon  of  oil.  On  the  other  hand,  the 
power  of  a  catadioptric  light  of  the  first  order,  like  that  lately 
established  at  Girdleness,  may  be  estimated  thus :  The  mean  effect 
of  the  light  produced  by  the  joint  effect  of  both  the  dioptric  and 
catadioptric  parts  of  fixed  light  apparatus,  may  be  valued  at  450 
Argand  flames,  which,  multiplied  by  360  degrees,  gives  an  aggregate 
of  162,000  ;  and  if  this  quantity  be  divided  by  570  (the  number  of 
gallons  burned  by  the  great  flame  in  a  year )  we  shall  have  about 
284  Argand  flames  for  the  effect  of  the  light  produced  by  the  com- 
bustion of  a  gallon  of  oil.  It  would  thus  appear  that  in  fixed  lights, 
the  French  apparatus,  as  lately  improved,  produces,  as  the  average 
effect  of  the  combustion  of  the  same~quantity  of  oil  over  the  whole 
horizon,  upwards  of  four  times  the  amount  of  light  that  is  obtained 
by  the  catoptric  mode. 

But  the  great  superiority  of  the  dioptric  method  chiefly  rests  upon 


198 

its  perfect  fulfilment  of  an  important  condition  required  in  a  fixed 
light,  by  distributing  the  rays  equally  in  every  point  of  the  horizon. 
In  the  event  of  the  whole  horizon  not  requiring  to  be  illuminated, 
the  dioptric  light  would  lose  a  part  of  its  superiority  in  economy, 
and  when  half  the  horizon  only  is  lighted,  it  would  be  more  expen- 
sive than  the  reflected  light ;  but  the  greater  power  and  more  equal 
distribution  of  the  light  may  be  considered  of  so  great  importance, 
as  far  to  outweigh  the  difference  of  expense.  In  the  latter  case,  too, 
an  additional  power,  as  already  noticed,  can  be  given  to  the  dioptric 
light,  by  placing  at  the  landward  side  of  the  light  room,  spherical 
mirrors  with  their  centres  in  the  focus  of  the  refracting  apparatus.* 
The  luminous  cones,  or  pyramids,  of  which  such  reflectors  would 
form  the  bases,  instead  of  passing  off  uselessly  to  the  land,  would 
thus  be  thrown  back  through  the  focal  point,  and  finally  refracted, 
so  as  to  increase  the  effect  of  the  light  seaward  by  nearly  one-third 
of  the  light  which  would  otherwise  be  lost. 

The  expense  of  establishing  a  fixed  light  composed  of  twenty-six 
reflectors  may  be  estimated  at  £950,  and  its  annual  maintenance, 
including  interest  on  the  first  cost  of  the  apparatus,  may  be  reckoned 
at  £425  10s. ;  and  the  expense  of  fitting  up  a  fixed  light  on  the  diop- 
tric principle  with  catadioptric  zones  is  £1,511,  while  its  annual 
maintenance  may  be  taken  at  £285  6s.  4c?.  It  thus  appears  that  the 
annual  expenditure  of  dioptric  fixed  light  is  £140  3s.  Sd.  less  than 
that  of  a  fixed  light  composed  of  twenty-six  reflectors ;  while  the 
average  effect,  equally  diffused  over  the  horizon,  is  four  times  greater. 

The  comparative  views  already  given  of  the  catoptric  and  dioptric 
modes  of  illuminating  light-houses,  demonstrate  that  the  latter  pro- 
duces more  powerful  lights  by  the  combustion  of  the  same  quantity 
of  oil ;  while  it  is  obvious  that  the  catoptric  system  insures  a  more 
certain  exhibition  of  the  light,  from  the  fountain  lamps  being  less 
liable  to  derangement  than  the  mechanical  lamps  used  in  dioptric 
lights.  The  balance,  therefore,  of  real  advantages  or  disadvantages, 
and  consequently  the  propriety  of  adopting  the  one  or  the  other 
system,  involves  a  mixed  question,  not  susceptible  of  a  very  precise 
solution,  and  leaving  room  for  different  decisions,  according  to  the 

0  A  similar  arrangement  can  also  be  made  in  revolving  lights  by  making  the  radius  of 
the  mirrors  somewhat  less  than  that  of  the  inscribed  circle  of  the  octagon  bounded  by  the 
lenses,  so  that  they  may  circulate  freely  round  the  backs  of  the  mirrors.  The  shortness 
of  the  radius  of  the  reflecting  surface  would,  of  course,  increase  the  divergence  of  the  beam 
of  light  refracted  through  the  lenses,  as  the  flame  would,  in  this  case,  subtend  a  greater 
angle  at  the  face  of  the  mirrors. 


199 

value  which  may  be  set  upon  obtaining  a  cheaper  and  better  light 
on  the  one  hand,  as  contrasted,  on  the  other,  with  less  certainty  in 
its  exhibition.  Experience,  however,  goes  far  to  show  that,  in  prac- 
tice, the  risk  of  extinction  of  the  lamp  in  dioptric  lights  is  very 
small. 

A  few  general  considerations,  serving  briefly  to  recapitulate  the 
arguments  for  and  against  the  two  systems,  may  not  be  out  of  place. 
And,  first,  regarding  the  fitness  of  dioptric  instruments  for  revolving 
lights,  it  appears  from  the  details  above  given — 

1.  That  by  placing  eight  reflectors  on  each  face  of  a  revolving 
frame,  a  light  might  be  obtained  as  brilliant  as  that  derived  from  the 
great  annular  lens ;   and  that,  in  the  case  of  a  frame  of  three  sides, 
the  excess  of  expense  by  the  reflecting  mode  would  be  £63  18s. ; 
and  in  the  case  of  a  frame  of  four  sides,  the  excess  would  amount 
to  £225. 

2.  That  for  burning  oil  economically  in  revolving  light-houses, 
which  illuminate  every  point  of  the  horizon  successively,  the  lens  is 
more  advantageous  than  the  reflector  in  the  ratio  of  3.6  to  1. 

3.  That  the  divergence  of  the  rays  from  the  lens  being  less  than 
from  the   reflector,   it  becomes  difficult  to  produce,  by  lenses,  the 
appearance  which  characterizes  the  catoptric  revolving  lights,  already 
so  well  known  to  British  mariners;  and  any  change  of  existing  lights 
which  would,  of  course,  affect  their  appearance,   must,  therefore, 
involve  some  practical  objections,  which  do  not  at  all  apply  to  the 
case  of  new  lights. 

4.  That  the  uncertainty  in  the  management  of  the  lamp  renders  it 
more  difficult  to  maintain  the  revolving  dioptric  lights  without  risk 
of  extinction — an  accident  which  has  several  times  occurred  at  Cor- 
douan  and  other  light-houses,   both  in  Prance  and  elsewhere.     A 
more   extended  experience,  however,   has  tended  to  moderate  any 
fears  on  this  head. 

5.  That  the  extinction  of  one  lamp  in  a  revolving  catoptric  light 
is  not  only  less  probable,  but  leads  to  much  less  serious  consequences 
than  the  extinction  of  the  single  lamp  in  a  dioptric  light ;   because, 
in  the  first  case,  the  evil  is  limited  to  diminishing  the  power  of  one 

face  by  an  eighth  part ;  whilst,  in  the  second,  the  ivliole  horizon  is 
totally  deprived  of  light.  The  extinction  of  a  lamp,  therefore,  in  a 
dioptric  light,  leads  to  evils  which  may  be  considered  very  great  in 
comparison  with  the  consequences  which  attend  the  same  accident 
in  a  catoptric  light. 


200 

In  comparing  the  fixed  dioptric  and  the  fixed  catoptric  apparatus, 
the  results  may  be  summed  up  under  the  following  heads  : 

1.  It  is  impossible,  by  means  of  any  practicable   combination  of 
paraboloi'dal  reflectors,  to  distribute  round  the  horizon  a  zone  of  light 
of  exactly  equal  intensity  ;  while  this  may  be  easily  effected  by  diop- 
tric means,  in  the  manner  already  described.     In  other  words,  the 
qualities  required  in  fixed  lights  cannot  be  so  fully  obtained  by  reflect- 
ors as  by  refractors. 

2.  The  average  light  produced  in  every  azimuth  by  burning  one 
gallon  of  oil  in  Argand  lamps,  with  reflectors,  is  only  about  one-fourth 
of  that  produced  by  burning  the  same  quantity  in  the  dioptric  appa- 
ratus ;  and  the  annual  expenditure  is  X140  3s.  Sd,  less  for  the  entire 
dioptric  light  than  for  the  catoptric  light. 

3.  The  characteristic  appearance  of  the  fixed  reflecting  light  in  any 
one  azimuth  would  not  be  changed  by  the  adoption  of  the  dioptric 
method,  although  its  increased  mean  power  would  render  it  visible 
at  a  greater  distance  in  every  direction. 

4.  From  the  equal  distribution  of  the  rays,  the  dioptric  light  would 
be  observed  at  equal  distances  in  every  point  of  the  horizon;  an  effect 
which  cannot  be  fully  attained  by  any  practicable  combination  of  para- 
boloi'dal reflectors. 

5.  The  inconveniences  arising  from  the  uncertainty  which  attends 
the  use  of  the  mechanical  lamp,  are  not  perhaps  so  much  felt  in  a 
fixed  as  in  a  revolving  light;  because  the  greater  simplicity  of  the 
apparatus  admits  of  easier  access  to  it  in  case  of  accident. 

6.  But  the  extinction  of  a  lamp  in  a  catoptric  light,  leaves  only  one 
twenty -sixth  part  of  the  horizon  without  the  benefit  of  the  light,  and 
the  chance  of  accident  arising  to  vessels  from  it,  may,  therefore,  be 
considered  as  incalculably  less  than  the  danger  resulting  from  the 
extinction  of  the  single  lamp  of  the  dioptric  light,  which  deprives 
the  whole  horizon  of  light. 

7.  There  is  also,  in  certain  situations,  a  risk  arising  from  irregu- 
larity in  the  distances  at  which  the  same  fixed  catoptric  light  can  be 
seen  in  the  different  azimuths.     This  defect,  of  course,  does  not  exist 
in  the  dioptric  light. 

There  can  be  little  doubt  that  the  more  fully  the  system  of  Fresnel 
is  understood,  the  more  certainly  will  it  be  preferred  to  the  catoptric 
system  of  illuminating  light-houses,  at  least  in  those  countries  where 
this  important  branch  of  administration  is  conducted  with  the  care 
and  solicitude  which  it  deserves. 


It  must  not,  however,  be  imagined,  that  there  are  no  circumstances 
in  which  the  catoptric  system  is  not  absolutely  preferable  to  illumi- 
nation by  means  of  lenses.  We  have  hitherto  attended  only  to  hori- 
zontal divergence  and  its  effects,  and  this  is  unquestionably  the  more 
important  view;  but  the  consideration  of  vertical  divergence  must 
not  be  altogether  overlooked.  Now  while  it  is  obvious  that  vertical 
divergence,  at  least  above  the  horizon,  involves  a  total  loss  of  the 
light  which  escapes  uselessly  upwards  into  space,  (in  which  respect 
the  reflectors  are  much  less  advantageous,)  it  is  no  less  true,  that  if 
the  sheet  of  light  which  reaches  the  most  distant  horizon  of  the  light- 
house, however  brilliant,  were  as  thin  as  the  absence  of  all  vertical 
divergence  would  imply,  it  would  be  practically  useless;  and  some 
measure  of  dispersion  in  the  arc  below  the  horizon  is  therefore  ab- 
solutely indispensable  to  constitue  a  really  useful  light.  In  the  re- 
flector, the  greatest  vertical  divergence  below  the  horizontal  plane 
of  the  focus  is  16°  8',  and  that  of  the  lens  is  about  4°  30'.  Let  us 
consider  for  a  moment  the  bearing  of  those  facts  upon  the  applica- 
tion of  the  two  modes  of  illumination  to  special  circumstances.  The 
powerful  beam  of  light  transmitted  by  the  lens  peculiarly  fits  that 
instrument  for  the  great  sea-lights  which  are  intended  to  warn  the 
mariner  of  his  approach  to  a  distant  coast  which  he  first  makes  on  an 
over-sea  voyage ;  and  the  deficiency  of  its  divergence,  whether  hori- 
zontal or  vertical,  is  not  practically  felt  as  an  inconvenience  in  lights 
of  that  character,  which  seldom  require  to  serve  the  double  purpose 
of  being  visible  at  a  great  distance,  and  at  the  same  time  of  acting  as 
guides  for  danger  near  the  shore.  For  such  purposes,  the  lens  applies 
the  light  much  more  advantageously  as  well  as  more  economically  than 
the  reflector;  because,  while  the  duration  of  its  least  divergent  beam 
is  nearly  equal  to  that  of  the  reflector,  it  is  eight  times  more  power- 
ful. A  revolving  system  of  eight  lenses  illuminates  an  horizontal 
arc  of  32°  with  this  bright  beam.  The  reflector,  on  the  other  hand, 
spreads  the  light  over  a  larger  arc  of  the  horizon;  and,  while  its  least 
divergent  beam  is  much  less  powerful  than  that  of  the  lens,  the  light 
which  is  shed  over  its  extreme  arc  is  so  feeble  as  to  be  practically  of 
no  use  in  lights  of  extensive  range,  even  during  clear  weather.  When 
a  light-house  is  placed  on  a  very  high  headland,  however,  the  defi- 
ciency of  divergence  in  the  vertical  direction  is  often  found  to  be 
productive  of  some  practical  inconvenience;  but  this  defect  may  be 
partially  remedied  by  giving  to  the  lenses  a  slight  inclination  out- 
wards from  the  vertical  plane  of  the  focus,  so  as  to  cause  the  most 


202 

brilliant  portion  of  the  emergent  beam  to  reach  the  visible  horizon 
which  is  due  to  the  height  of  the  lantern.  It  may  be  observed,  also, 
that  a  lantern  at  the  height  of  150  feet,  which  (taking  into  account 
the  common  height  of  the  observer's  eye  at  sea)  commands  a  range  of 
upwards  of  twenty  English  miles,  is  sufficient  for  all  the  ordinary  pur- 
poses of  the  navigator,  and  that  the  intermediate  space  is  practically 
easily  illuminated,  even  to  within  a  mile  of  the  light-house,  by  means 
of  a  slight  inclination  of  the  subsidiary  mirrors,  even  where  the  light 
from  the  principal  part  of  the  apparatus  passes  over  the  seaman' s  head. 
For  the  purpose  of  leading  lights,  in  narrow  channels,  on  the  other 
hand,  and  for  the  illumination  of  certain  narrow  seas,  there  can  be 
no  doubt  that  reflectors  are  much  more  suitable  and  convenient.  In 
such  cases,  the  amount  of  vertical  divergence  below  the  horizon 
forms  an  important  element  in  the  question,  because  it  is  absolutely 
necessary  that  the  mariner  should  keep  sight  of  the  lights  even  when 
he  is  very  near  them;  while  there  is  not  the  same  call  for  a  very 
powerful  beam  which  exists  in  the  case  of  sea-lights.  Yet  even  in 
narrow  seas,  where  low  towers,  corresponding  to  the  extent  of  the 
range  of  the  light,  are  adopted,  but  where  it  is,  at  the  same  time, 
needful  to  illuminate  the  whole  or  the  greater  part  of  the  horizon, 
the  use  of  dioptric  instruments  will  be  found  almost  unavoidable, 
especially  in  fixed  lights,  as  well  from  their  equalizing  the  distri- 
bution of  the  light  in  every  azimuth,  as  from  their  much  greater  econ- 
omy in  situations  where  a  large  annual  expenditure  would  often  be 
disproportionate  to  the  revenue  at  disposal.  In  such  places,  where 
certain  peculiarities  of  the  situation  require  the  combination  of  a  light 
equally  diffused  over  the  greater  portion  of  the  horizon,  along  with  a 
greater  vertical  divergence  in  certain  azimuths,  than  dioptric  instru- 
ments afford,  I  have  found  it  convenient  and  economical  to  add  to  the 
fixed  refracting  apparatus  a  single  paraboloidal  reflector  in  order  to 
produce  the  desired  effect,  instead  of  adapting  the  whole  to  the  more 
expensive  plan  for  the  sake  of  meeting  the  wants  of  a  single  narrow 
sector  of  its  range.  In  other  cases,  where  the  whole  horizon  is  to  be 
illuminated,  and  great  vertical  divergence  is  at  the  same  time  desi- 
rable, a  slight  elevation  of  the  burner,  at  the  expense,  no  doubt,  of 
a  small  loss  of  light,  is  sometimes  resorted  to,  and  is  found  to  pro- 
duce, with  good  effect,  the  requisite  depression  of  the  emergent  rays. 
In  certain  situations,  where  a  great  range,  and,  consequently,  a 
powerful  light  must  be  combined  with  tolerably  powerful  illumina- 
tion in  the  immediate  vicinity  of  the  light-house,  we  might,  perhaps, 


203 

advantageously  adopt  a  variation  of  the  form  and  dimensions  of  the 
mirrors  employed,  so  as  to  resemble  those  formerly  used  at  the  Tour 
de  Cordouan,  which  were  of  considerably  larger  surface  and  longer 
focal  distance  than  those  which  are  used  in  Britain.  If  such  a  form 
were  adopted,  the  power  of  the  light  for  the  purpose  of  the  distant 
range  would  be  increased  ;  and  I  would  propose  to  compensate  for 
the  deficiency  of  divergence  consequent  on  a  long  focal  distance,  by 
placing  a  second  burner  in  some  position  between  the  parameter  and 
the  vertex,  and  slightly  elevated  above  the  axis  of  the  instrument,  so 
as  to  throw  the  greater  portion  of  the  beam  resulting  from  this  second 
burner  below  the  horizontal  plane  of  the  focus.  Such  an  expedient 
is  no  doubt  somewhat  clumsy,  and  would  at  the  same  time  involve  the 
consumption  of  twice  the  quantity  of  oil  used  in  an  ordinary  catoptric 
light;  but  I  can  still  conceive  it  to  be  preferable,  in  certain  situations, 
to  the  use  of  the  lenses  alone. 

Thus  it  appears  that  we  must  not  too  absolutely  conclude  against 
one,  or  in  favor  of  the  other  mode  of  illumination  for  light-houses; 
but,  as  in  every  other  department  of  the  arts,  we  shall  find  the  neces- 
sity of  patiently  weighing  all  the  circumstances  of  each  particular 
case  that  comes  before  us,  before  selecting  that  instrument,  or  com- 
bination of  instruments,  which  appears  most  suitable. 

The  mode  of  distinguishing  lights  in  the  system  of  Fresnel  depends 
more  upon  their  magnitude  and  the  measured  interval  of  the  time  of 
their  revolution,  than  upon  their  appearance;  and  no  other  very 
marked  distinctions,  except  fixed  and  revolving,  have  been  success- 
fully attempted  in  France.  As  above  stated,  I  consider  the  distinc- 
tion of  the  fixed  light  varied  by  flashes,  to  possess  an  appearance  too 
slightly  differing  from  that  of  a  revolving  light,  to  admit  of  its  being 
safely  adopted  in  situations  where  revolving  lights  are  near.  The 
trial  which  I  made  at  the  Little  Ross,  in  the  Solway  Frith,  of  pro- 
ducing, by  means  of  lenses,  a  light  flashing  once  in  five  seconds  of 
time,  although  successful  so  far  as  mere  distinction  is  concerned,  has 
several  practical  defects,  arising  from  the  shortness  of  the  duration 
of  the  flashes  compared  with  the  powerful  effect  of  the  fixed  part  of 
the  apparatus,  which  I  consider  sufficient  to  prevent  its  adoption  in 
future,  especially  considering  that  a  much  more  marked  appearance 
can  be  produced  by  means  of  reflectors,  as  has  been  done  at  the 
Buchanness  in  Aberdeenshire,  and  the  Rhinns  of  Islay  in  Argyle- 
shire.  Colored  media  have  never,  so  far  as  I  know,  been  applied  to 
dioptric  apparatus,  except  in  the  case  of  the  Maplin  light  at  the 


204 

mouth  of  the  Thames,  and  Cromarty  Point  light  at  the  entrance  to 
the  Cromarty  Frith,  Nosshead  in  Caithness,  and  Ship  Rock  of  Sanda 
in  Argyleshire,  but  in  all  those  instances  successfully.  In  the  case 
of  the  fixed  light  at  Sanda,  in  particular,  I  would  observe  that  it  is 
seen  at  the  distance  of  sixteen  nautical  miles,  and  occasionally 
observed  even  so  far  off  as  twenty-two  nautical  miles.  The  enormous 
loss  of  light,  however,  amounting  to  no  less  than  0-80  of  the  whole 
incident  rays,  forms  a  great  bar  to  the  adoption  of  color  as  a  distinc- 
tion; and  any  means  which  could  tend  to  lessen  that  absorption,  and 
at  the  same  time  produce  the  characteristic  appearance,  would  be 
most  valuable.  I  have  tried  some  glasses  of  a  pink  tinge,  prepared 
by  M.  Letourneau  of  Paris,  in  which  the  absorption  does  not  exceed 
0-57  of  the  incident  rays;  but  the  appearance  of  the  light,  at  a  dis- 
tance, is  much  less  marked  than  that  produced  by  the  glasses  used 
in  Britain.  Such  deficiency  of  characteristic  color  might  lead  to 
serious  consequences,  as  the  transmission  of  white  rays,  through  a 
hazy  atmosphere,  too  often  produces,  by  absorption,  a  reddish  tinge 
of  the  light,  for  which  the  less  marked  appearance  given  by  the 
paler  media  might  be  easily  mistaken.  This  coloring  power  of 
absorption  is  so  well  known,  that  red  lights  are  seldom  used  except 
in  direct  contrast  with  white  ones;  but,  on  a  coast  so  thickly  studded 
with  light-houses  as  that  of  Great  Britain,  the  number  of  distinctions 
is  insufficient  to  supply  all  our  wants,  so  that  we  are  sometimes  reluc- 
tantly compelled  to  adopt  a  single  red  light  in  some  situation  of  lesser 
importance,  or  which,  from  some  local  circumstances  and  the  appear- 
ance of  the  lights  which  must  be  seen  by  the  mariner  before  passing 
it,  is  not  likely  to  be  mistaken  for  any  other.  The  great  loss  of  light 
by  colored  media  causes  the  red  beam,  in  a  revolving  light,  to  be 
seen  at  a  shorter  distance  than  the  white;  and  it  is  conceivable  that, 
in  certain  circumstances,  this  might  lead  the  mariner  to  mistake  a 
red  and  white  light  for  a  white  light  revolving  at  half  the  velocity. 
Such  a  mistake  might  perhaps  prove  dangerous;  but  the  lights  are 
generally  so  situated  that  there  is  ample  time  for  the  mariner,  after 
first  discovering  the  red  light,  and  thus  correcting  any  mistake,  to 
shape  his  course  accordingly.  All  other  colored  media,  except  red, 
have  been  found  useless  as  distinctions  for  any  lights  of  extensive 
range,  and  fail  to  be  efficient,  owing  to  the  necessity  of  absorbing 
almost  all  the  light  before  a  marked  appearance  can  be  obtained.  In 


a  few  pier  or  ferry  lights,  green  and  blue  media  have  been  tried,  and 
found  available  at  the  distance  of  a  few  cables'  lengths.* 

It  seems  to  be  a  natural  consequence  of  the  physical  distribution 
of  light,  that  fixed  lights,  which  illuminate  the  whole  horizon,  should 
be  less  powerful  than  revolving  lights  which  have  their  effect  con- 
centrated within  narrow  sectors  of  the  horizon.  Any  attempt  to 
increase  the  power  of  fixed  lights  is,  therefore,  worthy  of  attention; 
and  when  the  late  Captain  Basil  Hall  proposed  a  plan  for  effecting 
this  object,  it  received,  as  it  deserved,  the  full  consideration  of  the 
Scotch  Light-house  Board,  who  authorized  me  to  repeat  Captain  Hall's 
experiments,  and  verify  his  results  by  observations  made  at  a  consid- 
erable distance. 

The  familiar  experiment  of  whirling  a  burning  stick  quickly  round 
the  head,  so  as  to  produce  a  ribbon  of  light,  proves  the  possibility  of 
causing  a  continuous  impression  on  the  retina  by  intermittent  images 
succeeding  each  other  with  a  certain  rapidity.  From  the  moderate 
velocity  at  which  this  continuity  of  impression  is  obtained,  we  should 
be  warranted  in  concluding,  a  priori,  that  the  time  required  to  make 
an  impression  on  the  retina  is  considerably  less  than  the  duration  of 
the  impression  itself ;  for  the  continuity  of  effect  must,  of  course,  be 
caused  by  fresh  impulses  succeeding  each  other  before  the  preceding 
ones  have  entirely  faded.  If  it  were  otherwise,  and  the  time  required 
to  make  the  impression  were  equal  to  the  duration  of  the  sensation, 
it  would  obviously  be  impossible  to  obtain  a  series  of  impulses  so 
close  or  continuous  in  their  effect  as  to  run  into  and  overlap  each 
other,  and  thus  throw  out  the  intervals  of  darkness ;  because  the 
same  velocity  which  would  tend  to  shorten  the  dark  intervals,  would 
also  curtail  the  bright  flashes,  and  thus  prevent  their  acting  on  the 
eye  long  enough  to  cause  an  impression.  Accordingly,  we  find  that 
the  duration  of  an  impression  is  in  reality  much  greater  than  the 
time  required  for  producing  the  effect  on  the  retina.  It  is  stated  by 
Professor  Wheatstone,  in  the  London  Transactions  for  1834,  that  only 
about  one  millionth  part  of  a  second  is  required  for  making  a  distinct 
impression  on  the  eye;  and  it  appears  from  a  statement  made  by  Lame, 
at  p.  425  of  his  Cours  de  Physique,  that  M.  Plateau  found  that  an 
impression  on  the  retina  preserves  its  intensity  unabated  during  one 

~  In  some  late  experiments  which  I  made  with  very  powerful  instruments,  green  lights 
were  visible,  in  very  clear  weather,  at  the  distance  of  seven  miles.  The  blue  could  only 
once  be  seen,  with  great  difficulty,  at  five  miles. 


206 

hundredth  of  a  second,  so  that,  however  small  those  times  may  be  in 
themselves,  the  one  is  ten  thousand  times  greater  than  the  other. 

It  has  been  ascertained,  by  direct  experiment,*  that  the  eye  can 
receive  a  fresh  impression  before  the  preceding  one  has  faded  ;  and, 
indeed,  if  this  were  impossible,  absolute  continuity  of  impression 
from  any  succession  of  impulses,  however  rapid,  would  seem  to  be 
unattainable;  and  the  approach  to  perfect  continuity  would  be  in- 
versely at  the  time  required  to  make  an  impression. 

From  the  property  Avhich  bright  bodies  passing  rapidly  before  the 
eye  possess  of  communicating  a  continuous  impression  to  the  sense 
of  sight,  the  late  Captain  Basil  Hall  conceived  the  idea,  not  merely 
of  obtaining  all  the  effects  of  a  fixed  light,  by  causing  a  system  of 
lenses  to  revolve  with  such  a  velocity  as  to  produce  a  continuous  im- 
pression, but,  at  the  same  time,  of  obtaining  a  much  more  brilliant 
appearance,  by  the  compensating  influence  of  the  bright  flashes, 
which  he  expected  would  produce  impulses  sufficiently  powerful  and 
durable  to  make  the  deficiency  of  light  in  the  dark  spaces  almost 
imperceptible.  The  mean  effect  of  the  whole  series  of  changes 
would,  he  imagined,  be  thus  greatly  superior  to  that  which  can  be 
obtained  from  the  same  quantity  of  light  equally  distributed,  as  in 
fixed  lights,  over  the  whole  horizon.  Now  this  expectation,  if  it  be 
considered  solely  in  reference  to  the  physical  distribution  of  the 
light,  involves  various  difficulties.  The  quantity  of  light  subjected 
to  instrumental  action  is  the  same  whether  we  employ  the  refracting 
zones  at  present  used  in  fixed  dioptric  lights,  or  attempt  to  obtain 
continuity  of  effect  by  the  rapid  revolution  of  lenses  ;  and  the  only 
difference  in  the  action  of  those  two  arrangements  is  this,  that  while 
the  zones  distribute  the  light  equally  over  the  whole  horizon,  or 
rather  do  not  interfere  with  its  natural  horizontal  distribution,  the 
effect  of  the  proposed  method  is  to  collect  the  light  into  pencils, 
which  are  made  to  revolve  with  such  rapidity  that  the  impression 
from  each  pencil  succeeds  the  preceding  one  in  time  to  prevent  a 
sensible  occurrence  of  darkness.  To  expect  that  the  mean  effect  of 
the  light,  so  applied,  should  be  greater  than  when  it  is  left  to  its 
natural  horizontal  divergence,  certainly  appears  at  first  to  involve 
something  approaching  to  a  contradiction  of  physical  laws.  In  both 

3  Lame,  Cours  de  Phyrique,  p.  424.  "  L' impression  peut  subdster  encore  lorsque  la 
suivantc  a  lien." 


207 

cases,  the  same  quantity  of  light  is  acted  upon  by  the  instrument; 
and,  in  either  case,  any  one  observer  will  receive  an  impression  sim- 
ilar and  equal  to  that  received  by  any  other  stationed  at  a  different 
part  of  the  horizon ;  so  that,  unless  we  imagine  that  there  is  some 
loss  of  light  peculiar  to  one  of  the  methods,  we  are  shut  up,  in  the 
physical  view  of  the  question,  to  the  conclusion  that  the  impressions 
received  by  each  class  of  observers  must  be  of  equal  intensity.  In 
other  words,  the  same  quantity  of  light  is  by  both  methods  employed 
to  convey  a  continuous  impression  to  the  senses  of  spectators  in  every 
direction,  and,  in  both  methods,  equality  of  distribution  is  effected, 
since  it  does  not  at  all  consist  with  our  hypothesis,  that  any  one  ob- 
server in  the  same  class  should  receive  more  or  less  than  his  equal 
share  of  the  light.  Then,  as  to  the  probability  of  the  loss  of  light, 
it  seems  natural  to  expect  that  this  should  occur  in  connection  with 
the  revolving  system,  because  the  velocity  is  an  extraneous  circum- 
stance, by  no  means  necessary  to  an  equal  distribution  of  the  light, 
which  can,  as  we  already  know,  be  more  naturally,  and  at  the  same 
time  perfectly  attained  by  the  use  of  the  zones. 

On  the  other  hand,  it  must  not  be  forgotten  that,  although  the 
effect  of  both  methods  is  to  give  each  part  of  the  horizon  an  equal 
share  of  light,  there  is  yet  this  difference  between  them,  that  while 
the  light  from  the  zones  is  equally  intense  at  every  instant  of  time, 
that  evolved  by  the  rapidly  circulating  lenses  is  constantly  passing 
through  every  phase  between  total  darkness  and  the  brightest  flash 
of  the  lens  ;  and  this  difference,  taken  in  connection  with  some  curi- 
ous physiological  observations  regarding  the  sensibility  of  the  retina, 
gives  considerable  countenance  to  the  expectation  on  which  Captain 
Hall's  ingenious  expedient  is  based.  The  fact  which  has  already 
been  noticed,  and  which  the  beautiful  experiments  of  M.  Plateau 
and  Professor  Wheatstone  have  of  late  rendered  more  precise,  that 
the  duration  of  an  impression  on  the  retina  is  not  only  appreciable, 
but  is  much  greater  than  the  time  required  to  cause  it,  seems  to  en- 
courage us  in  expecting  that,  while  the  velocity  required  to  produce 
continuity  of  effect  would  not  be  found  so  great  as  to  interfere  with 
the  formation  of  a  full  impression,  the  duration  of  the  impulse  from 
each  flash  would  remain  unaltered,  and  the  dark  intervals  which  do 
not  excite  the  retina  would,  at  the  same  time,  be  shortened ;  and 
that,  therefore,  we  might,  in  this  manner,  obtain  an  effect  on  the 


208 

senses  exceeding  the  brilliancy  of  a  steady  light  distributed  equally 
in  every  direction  by  the  ordinary  method.  Some  persons,  indeed, 
who  have  speculated  on  this  subject,  seem  even  to  be  of  opinion. 
that  so  far  from  the  whole  effect  of  the  series  of  continuous  impres- 
sions being  weakened  by  a  blending  of  the  dark  with  the  bright 
intervals,  the  eye  would  in  reality  be  stimulated  by  the  contrast  of 
light  and  darkness,  so  as  thereby  to  receive  a  more  complete  and 
durable  impulse  from  the  light.  It  is  obvious,  however,  that  this 
question  regarding  the  probable  effect  to  be  anticipated  from  a  revo- 
lution so  rapid  as  to  cause  a  continuous  impression,  could  only  have 
been  satisfactorily  answered  by  appeal  to  experiment. 

In  experimenting  on  this  subject,  I  used  the  apparatus  formerly 
employed  by  Captain  Hall.  It  consisted  of  an  octagonal  frame, 
which  carried  eight  of  the  discs  that  compose  the  central  part  of 
Fresnel's  compound  lens,  and  was  susceptible  of  being  revolved 
slowly  or  quickly  at  pleasure,  by  means  of  a  crank  handle  and  some 
intermediate  gearing.  The  experiments  were  nearly  identical  with 
those  made  by  Captain  Hall,  who  contrasted  the  effect  of  a  single 
lens  at  rest,  or  moving  very  slowly,  with  that  produced  by  the 
eight  lenses,  revolving  with  such  velocity  as  to  cause  an  apparently 
continuous  impression  on  the  eye.  To  this  experiment  I  added  that 
of  comparing  the  beam  thrown  out  by  the  central  portion  of  a  cylin- 
dric  refractor,  such  as  is  used  at  the  fixed  light  of  the  Isle  of  May, 
with  the  continuous  impression  obtained  by  the  rapid  revolution  of 
the  lenses.  Captain  Hall  made  all  his  comparisons  at  the  short  dis- 
tance of  one  hundred  yards;  and,  in  order  to  obtain  some  measure  of 
the  intensity,  he  viewed  the  lights  through  plates  of  colored  glass 
until  the  luminous  discs  became  invisible  to  the  eye.  I  repeated 
those  experiments  at  Gullan,  under  similar  circumstances,  but  with 
very  different  results.  I  shall  not,  however,  enter  upon  the  discus- 
sion of  those  differences  here,  although  they  are  susceptible  of 
explanation,  and  are  corroborative  of  the  conclusions  at  which  I 
arrived  by  comparing  the  lights  from  a  distance  of  fourteen  miles, 
but  shall  briefly  notice  the  more  important  results  which  were  ob- 
tained by  the  distant  view.  They  are  as  follows  : 

1.  The  flash  of  the  lens  revolving  slowly  was  very  much  larger 
than  that  of  the  rapidly  revolving  series;  and  this  decrease  of  size 
in  the  luminous  object  presented  to  the  eye  became  more  marked  as 


209 

the  rate  of  revolution  was  accelerated,  so  that,  at  the  velocity  of 
eight  or  ten  flashes  in  a  second  the  naked  eye  could  hardly  detect  it, 
and  only  few  of  the  observers  saw  it,  while  the  steady  light  from  the 
fixed  refractor  was  distinctly  visible. 

2.  There  was   also  a  marked  falling  off  in  the   brilliancy  of  the 
rapid  flashes  as  compared  with  that  of  the  slow  ones  ;  but  this  effect 
was  by  no  means  so  striking  as  the  decrease  of  volume. 

3.  Continuity  of    impression  was  not  attained  at  the  rate  of  five 
flashes  in  a  second,  but  each  flash  appeared  to  be  distinctly  sepa- 
rated by  an  interval  of  darkness  ;  and  even  when  the  nearest  ap- 
proach to  continuity  was  made,  by  the  recurrence  of  eight  or  ten 
flashes  in  a  second,  the  light  still  presented  a  twinkling  appearance, 
which  was  well  contrasted  with  the  steady  and  unchanging  effect  of 
the  cylindric  refractor. 

4.  The  light  of  the  cylindric  refractor  was,    as  already  stated, 
steady  and  unchanging,  and  of  much  larger  volume  than  the  rapidly 
revolving  flashes.     It  did  not,   however,  appear  so  brilliant  as  the 
flashes  of  the  quickly  revolving  lenses,  more  especially  at  the  lower 
rate  of  five  flashes  in  a  second. 

5.  When  viewed  through  a  telescope,  the  difference  of  volume  be- 
tween the  light  of  a  cylindric  refractor  and  that  produced  by  the 
lenses  at  their   greatest   velocity  was  very  striking.     The  former 
presented  a  large  diffuse  object  of  inferior  brilliancy,  while  the  lat- 
ter exhibited  a  sharp  pin-point  of  brilliant  light. 

Upon  a  careful   consideration  of  these   facts,  it  appears  warrant- 
able to  draw  the  following  general  conclusions  : 

1.  That  our  expectations  as  to  the  effects  of  light,  when  distrib- 
uted according  to  the  law  of  its  natural  horizontal  divergence,  are 
supported  by  observed  facts  as  to  the  visibility  of  such  lights,  con- 
trasted with  those  whose  continuity  of  effect  is  produced  by  collect- 
ing the  whole  light  into  bright  pencils,  and  causing  them  to  revolve 
with  great  velocity. 

2.  It  appears  that  this  deficiency  of  visibility  seems  to  be  chiefly 
due  to  a  want  of  volume  in  the  luminous  object,  and  also,  although  in 
a  less  degree,  to  a  loss  of  intensity,  both  of  which  defects  appear  to 
increase  in  proportion  as  the  motion  of  the  luminous  object  is  accel- 
erated. 

3.  That  this  deficiency  of  volume  is  the  most  remarkable  optical 

14 


210 

phenomenon  connected  with  the  rapid  motion  of  luminous  bodies, 
and  that  it  appears  to  be  directly  proportional  to  the  velocity  of 
their  passage  over  the  eye. 

4.  That  there  is  reason  to  suspect  that  the  visibility  of  distant 
light  depends  on  the  volume  of  the  impression  in  a  greater  degree 
than  has  perhaps  been  generally  imagined. 

5.  That,  as  the   size  and  intensity  of  the  radiants  causing  these 
various  impressions  to  a-  distant  observer  were  the  same,  the  volume 
of  the  light,  and,   consequently,  cceteris  paribus,  its  visibility,  are, 
within  certain  limits,  proportionate  to  the  time  during  which  the 
object  is  present  to  the  eye. 

Such  appear  to  be  the  general  conclusions  which  those  experi- 
ments warrant  us  in  drawing  ;  and  the  practical  result,  in  so  far  as 
light-houses  are  concerned,  is  sufficient  to  discourage  us  from  at- 
tempting to  improve  the  visibility  of  fixed  lights  in  the  manner  pro- 
posed by  Capt.  Hall,  even  supposing  the  practical  difficulties  con- 
nected with  the  great  centrifugal  force  generated  by  the  rapid  revo- 
lution of  the  lenses  to  be  less  than  they  really  are. 

The  decrease  in  the  volume  of  the  luminous  object  caused  by  the 
rapid  motion  of  the  lights  is  interesting  from  its  apparent  connec- 
tion with  the  curious  phenomenon  of  irradiation.  When  luminous 
bodies,  such  as  the  lights  of  distant  lamps,  are  seen  by  night,  they 
appear  much  larger  than  they  would  do  by  day  ;  and  this  effect  is 
said  to  be  produced  by  irradiation.  M.  Plateau,  in  his  elaborate 
essay  on  this  subject,  after  a  careful  examination  of  all  the  theories 
of  irradiation,  states  it  to  be  his  opinion,  that  the  most  probable 
mode  of  accounting  for  the  various  observed  phenomena  of  irradia- 
tion is  to  suppose,  that,  in  the  case  of  a  night-view,  the  excitement 
caused  by  light  is  propagated  over  the  retina  beyond  the  limits  of 
the  day-image  of  the  object,  owing  to  the  increased  stimulus  pro- 
duced by  the  contrast  of  light  and  darkness  j  and  he  also  lays  it 
down  as  a  law,  confirmed  by  numerous  experiments,  that  irradiation 
increases  with  the  duration  of  the  observation.  It  appears,  there- 
fore, not  unreasonable  to  conjecture,  that  the  deficiency  of  volume 
observed  during  the  rapid  revolution  of  the  lenses  may  have  been 
caused  by  the  light  being  present  to  the  eye  so  short  a  time,  that 
the  retina  was  not  stimulated  in  a  degree  sufficient  to  produce  the 
amount  of  irradiation  required  for  causing  a  large  visual  object. 


211 

When,  indeed,  the  statement  of  M.  Plateau,  that  irradiation  is  pro- 
portional to  the  duration  of  the  observation,  is  taken  in  connection 
with  the  observed  fact,  that  the  volume  of  the  light  decreased  as 
the  motion  of  the  lenses  was  accelerated,  it  seems  almost  impossible 
to  avoid  connecting  together  the  two  phenomena  as  cause  and  effect. 
Before  leaving  this  part  of  the  subject,  I  will  call  attention  to 
some  late  plans  for  combining  dioptric  and  catoptric  apparatus,  the 
object  of  which  is  to  subject  to  the  corrective  action  of  instruments, 
a  greater  proportion  of  the  luminous  sphere  than  it  has  yet  been 
found  practicable  to  do,  especially  in  revolving  lights.  Reflectors 
act  chiefly  on  the  posterior  portion  of  the  flame,  and  generally  re- 
ceive about  twelve-seventeenths  of  the  whole  luminous  sphere  ;  while 
a  series  of  dioptric  instruments  can  only  affect  an  anterior  zone, 
amounting  to  about  two-fifths  of  the  whole  light  which  is  emitted  by 
the  lamp.  Certain  deductions  due  to  the  form  of  the  lower  part  of 
the  burners,  and  to  the  loss  of  light  at  reflection,  which  is  not  less 
than  one-half  of  the  incident  light,  as  well  as  to  that  by  refraction 
through  the  lens,  (which,  however,  cannot  exceed  one-tenth  of  the 
incident  light,)  will  reduce  those  numbers  from  twelve-seventeenths 
to  one-third,  and  from  two-fifths  to  three-tenths,  thus  making  the 
ratio  of  the  proportion  of  the  whole  flame  actually  given  forth  by  the 
reflectors  to  the  amount  by  lenses  equal  to  that  of  ten  to  nine.  In 
fixed  lights,  on  Fresnel's  system,  we  have  already  seen  that  nearly 
the  whole  of  the  available  light  is  turned  to  a  useful  purpose  by 
means  of  the  curved  mirrors  or  catadioptric  zones,  which  are  added 
to  increase  the  effect  of  the  central  dioptric  belt ;  and,  in  revolving 
lights,  an  approximation  to  a  similar  result  is  obtained  by  the  addi- 
tion of  the  diacatoptric  combination  of  pyramidal  lenses  and  plane 
mirrors  placed  above  the  great  lenses.  Catoptric  lights,  however, 
to  which  such  auxiliary  arrangements  are  inapplicable,  had  still  the 
great  disadvantage  of  leaving  the  anterior  cone  of  light  to  pass  oft' 
in  the  useless  state  of  naturally  divergent  light ;  and  anything  cal- 
culated to  increase  the  power  of  that  class  of  lights,  without  alter- 
ing that  simplicity  and  security  of  the  burners  employed  in  them, 
which  renders  them  so  suitable  for  remote  situations  in  the  colonies, 
deserves  careful  attention.  It  will  be  remembered  that  the  propo- 
sal of  Mr.  Barlow  for  effecting  this  object,  has  already  been  noticed; 
and  it  is  needless  now  to  do  more  than  remind  the  reader  that  the 


212 

practical  disadvantage  of  the  great  aberration  in  the  path  of  the 
rays  reflected  from  the  subsidiary  hemispherical  mirror,  which  must 
necessarily  be  of  very  small  dimensions,  together  with  the  great 
loss  of  light  by  the  second  reflection,  must  go  far  to  neutralize  the 
effect  of  Mr.  Barlow's  plan.  A  combination  of  dioptric  and  catop- 
tric instruments,  intended  to  produce  a  similar  effect,  has  been  pro- 
posed by  Mr.  Alexander  Gordon,  and  is  described  at  page  385  of 
the  tenth  volume  of  the  Civil  Engineers'  and  Architects'  Journal.  It 
consists  of  a  paraboloi'dal  mirror,  of  a  very  short  focal  distance,  with 
some  of  the  outer  zones  of  one  of  Fresnel's  smaller  lenses  in  front 
of  it.  The  zones  are  intended  to  refract  some  of  the  rays  that  es- 
cape past  the  edges  of  the  mirror,  while  the  pencil  of  light  reflected 
from  the  mirror  itself  is  supposed  to  pass  through  the  circular  space 
which  is  generally  occupied  by  the  central  portion  of  the  lens.  This 
arrangement  is  a  step  in  the  right  direction,  only  in  so  far  as  it  im- 
plies the  union  of  the  two  modes  of  illumination  ;  but,  as  it  is  by  no 
means  skilfully  designed,  it  is  liable  to  several  palpable  objections. 

1.  The   actual   gain  of  light  has  been  greatly  overrated  by  the 
writer  in  the   Journal,   who   expects  to  turn  twenty-seven-twenty- 
eighths  of  the  whole  light  to  a  useful  account  ;  but  so  great  a  gain 
of  light  can  never  consist  with  the  form  and  position  of  the  lower 
part  of  the  flame. 

2.  Upwards  of  twenty-four-twenty-eighths  of  the  estimated  quan- 
tity would  be  intercepted  by  the  paraboloid  alone,  and  little  more 
than  two-twenty-eights  by  the  rings  of  the  lens,  an  addition  far  too 
insignificant  to  warrant  the  adoption  of  so   expensive  an  appendage 
to  the  reflector. 

3.  The  great  aberration  of  the  rays  reflected  by  the  conoid  behind 
the  parameter,  and  its  small  reflecting  surface,  must  render  it  prac- 
tically useless  ;  and.  perhaps,  nearly  one-half  of  the  whole  light  would 
thus  be  lost  to  the  mariner.     The  accurate  formation  of  a  paraboloid 
of  such  depth  would  also  be  difficult;  and,  considering  the  practical 
inutility  of  the  conoid  behind  the  parameter,  would  seem  to  be  a  mis- 
application of  labor. 

4.  The  union  of  such  an  instrument  with  the  lenticular  zones  in 
front,  which  require  that  the  pencil  of  parallel  rays  should  be  reflect- 
ed with  the  greatest  accuracy,  so  as  to  enable  them  to  pass  through 
the  circular  space  bounded  by  the  zones,  is  an  obvious  misapplica- 


213 

tion  of  a  paraboloid  with  a  short  focal  distance,  to  a  purpose  for 
which  it  is  singularly  unsuitable. 

5.  Mirrors  somewhat  of  the  same  form  were  in  use  at  Scilly  light- 
house, and  were  long  ago  discarded  as  disadvantageous,  at  the  sug- 
gestion of  the  late  eminent  Captain  Huddart. 

6.  The  outer  zones,  which  form  the  least  efficient,  and  at  the  same 
time  the  most  expensive  portion  of  the  compound  lens  have  been  pre- 
ferred to  the  central  portion  of  that  instrument  j  and  by  this  means 

the  anterior  cone  of  rays  is  at  the  same  time  lost. 

*  *  *  *  *  #  *  # 

A  considerable  practical  defect  in  all  the  light-house  lanterns  which 
I  have  ever  seen,  with  the  exception  of  those  recently  constructed  for 
the  Scotch  light-houses,  consists  in  the  vertical  direction  of  the  astra- 
gals, which  of  course  tend  to  intercept  the  whole  or  a  great  part  of 
the  light  in  the  azimuth  which  they  subtend.  The  consideration  of 
the  improvement  which  I  had  effected  in  giving  a  diagonal  direction 
to  the  joints  of  the  fixed  refractors  first  led  me  to  adopt  a  diagonal 
arrangement  of  the  framework  which  carries  the  cupola  of  zones,  and 
afterwards  for  the  astragals  of  the  lantern.  Not  only  is  the  direction 
of  the  astragals  more  advantageous  for  equalizing  the  effect  of  the 
light,  but  the  greater  stiffness  and  strength  which  such  an  arrange- 
ment gives  to  the  framework  of  the  lantern,  make  it  safe  to  use  more 
slender  bars,  and  thus  also  absolutely  less  light  is  intercepted  ;  the 
panes  of  glass  at  the  same  time  become  triangular,  and  are  necessarily 
stronger  than  rectangular  panes  of  equal  surface.  This  form  of  lan- 
tern is  extremely  light  and  elegant,  and  is  shown,  with  detailed 
drawings  of  some  of  its  principal  parts,  in  plate  X.  To  avoid  the 
necessity  of  painting,  which,  in  situations  so  exposed  as  those  which 
light-houses  generally  occupy,  is  attended  with  many  inconveniences 
and  no  small  risk,  the  framework  of  the  lantern  is  now  formed  of 
gun-metal  and  the  dome  is  of  copper.  A  lantern  for  a  light  of  the 
first  order,  twelve  feet  in  diameter,  and  with  glass  frames  ten  feet 
high,  costs,  when  glazed,  about  ,£1,260.  In  order  to  give  the  light- 
keepers  free  access  to  cleanse  and  wash  the  upper  panes  of  the  lan- 
tern, (an  operation  which  in  snowy  weather  must  sometimes  be  fre- 
quently repeated  during  the  night, )  a  narrow  gangway,  on  which 
they  may  safety  stand,  is  placed  on  the  level  of  the  top  of  the  lower 
panes,  and  at  the  top  of  the  second  panes  rings  are  provided  of  which 
the  light-keepers  may  lay  hold  for  security  in  stormy  weather.  A 
light  trap-ladder  is  also  attached  to  the  outside  of  the  lantern  by 


214 

means  of  which  there  is  an  easy  access  to  the  ventilator  on  the 
dome. 

Great  care  is  bestowed  on  the  glazing  of  the  lantern,  in  order  that 
it  may  be  quite  impervious  to  water,  even  during  the  heavy  gales. 
"When  iron  is  used  for  the  frames,  they  are  carefully  and  frequently 
painted  ;  but  gun-metal,  as  just  noticed,  is  now  generally  used  in  the 
Scotch  light-houses.  There  is  great  risk  of  the  glass  plates  being 
broken  by  the  shaking  of  the  lantern  during  high  winds;  and  as  much 
as  possible  to  prevent  this,  various  precautions  are  adopted.  The 
arris  of  each  plate  is  always  carefully  rounded  by  grinding  ;  and 
grooves  about  half  an  inch  wide,  capable  of  holding  a  good  thickness 
of  putty,  are  provided  in  the  astragals  for  receiving  the  glass,  which 
is  quarter  of  an  inch  thick.  Small  pieces  of  lead  or  wood  are  in- 
serted between  the  frames  and  the  plates  of  glass  against  which  they 
may  press,  and  by  which  they  are  completely  separated  from  the 
more  unyielding  material  of  which  the  lantern -frames  are  composed. 
Panes  glazed  in  frames  padded  with  cushions,  and  capable  of  being 
temporarily  fixed  in  a  few  minutes,  in  the  room  of  a  broken  plate, 
are  kept  ready  for  use  in  the  store-room.  Those  framed  plates  are 
called  storm  panes,  and  have  been  found  very  useful  on  several  occa- 
sions when  the  glass  has  been  shattered  by  large  sea-birds  coming 
against  it  in  a  stormy  night,  or  by  small  stones  violently  driven 
against  the  lantern  by  the  force  of  the  wind. 

The  ventilation  of  the  lanterns  forms  a  most  important  element  in 
the  preservation  of  a  good  and  sufficient  light.  An  ill-ventilated  lan- 
tern has  its  sides  continually  covered  with  the  water  of  condensation, 
which  is  produced  by  the  contact  of  the  ascending  current  of  heated 
air;  and  the  glass,  thus  obscured,  obstructs  the  passage  of  the  rays 
and  diminishes  the  power  of  the  light.  In  the  northern  light-houses, 
ventilators,  capable  of  being  opened  and  shut  at  pleasure,  so  as  to 
admit  from  without  a  supply  of  air  when  required,  are  provided  in 
the  parapet  wall  on  which  the  lantern  stands ;  the  lantern  roof  also 
is  surmounted  by  a  cover  which,  while  it  closes  the  top  of  an  open 
cylindric  tube  against  the  entrance  of  rain,  and  descends  over  it  only 
so  far  as  is  needful  for  that  purpose,  still  leaves  an  open  air-space 
between  it  and  the  dome.  This  arrangement  permits  the  current  of 
heated  air,  which  is  continually  flowing  from  the  lantern  through  the 
cylindric  tube,  to  pass  between  it  and  the  outer  cover,  from  which  it 
finally  escapes  to  the  open  air  through  the  space  between  the  cover 
and  the  dome.  The  door  which  communicates  from  the  light-room 


215 

through  the  parapet  to  the  balcony  outside,  is  also  made  the  means 
of  ventilating  the  light-room ;  and,  for  that  purpose,  it  is  provided 
with  a  sliding  bolt  at  the  bottom,  which,  being  dropped  into  one  or 
other  of  the  holes  cut  in  the  balcony  for  its  reception,  serves  to  keep 
the  door  open  at  any  angle  that  may  be  found  necessary.  A  useful 
precaution  was  introduced  by  my  predecessor,  as  engineer  to  the 
Northern  lights  Board,  in  order  to  prevent  the  too  rapid  condensa- 
tion of  heated  air  on  the  large  internal  surface  of  the  lantern  roof, 
which  consists  in  having  two  domes  with  an  air-space  between  them, 
as  shown  in  the  enlarged  diagrams  in  plate  X. 

An  important  improvement  in  the  ventilation  of  light-houses  was 
some  years  ago  introduced  by  Dr.  Faraday  into  several  of  the  light- 
houses belonging  to  the  Trinity  House,  and  has  since  been  adopted 
in  all  the  dioptric  lights  belonging  to  the  commissioners  of  Northern 
light-houses.  After  mentioning  several  proofs  of  extremely  bad 
ventilation  in  light-houses,  Dr.  Faraday  thus  describes  his  appa- 
ratus :* 

"The  ventilating  pipe  or  chimney  is  a  copper  tube,  four  inches  in 
diameter;  not,  however,  in  one  length,  but  divided  into  three  or  four 
pieces;  the  lower  end  of  each  of  these  pieces  for  about  one  and  a 
half  inch  is  opened  out  in  a  conical  form,  about  five  and  a  half  inches 
in  diameter  at  the  lowest  part.  When  the  chimney  is  put  together, 
the  upper  end  of  the  bottom  piece  is  inserted  about  half  an  inch  into 
the  cone  of  the  next  piece  above,  and  fixed  there  by  three  ties  or 
pins,  so  that  the  two  pieces  are  firmly  held  together;  but  there  is 
still  plenty  of  air-way  or  entrance  into  the  chimney  between  them. 
The  same  arrangement  holds  good  with  each  succeeding  piece. 
When  the  ventilating  chimney  is  fixed  in  its  place,  it  is  adjused  so 
that  the  lamp-chimney  enters  about  half  an  inch  into  the  lower  cone, 
and  the  top  of  the  ventilating  chimney  enters  into  the  cowl  or  head 
of  the  lantern. 

"With  this  arrangement,  it  is  found  that  the  action  of  the  venti- 
lating flue  is  to  carry  up  every  portion  of  the  products  of  combustion 
into  the  cowl ;  none  passes  by  the  cone  apertures  into  the  air  of  the 
lantern,  but  a  portion  of  the  air  passes  from  the  lantern  by  these  aper- 
tures into  the  flue,  and  so  the  lantern  itself  is  in  some  degree  ventilated. 

"  The  important  use  of  these  cone  apertures  is,  that  when  a  sudden 
gust  or  eddy  of  wind  strikes  into  the  cowl  of  the  lantern  it  should  not 
have  any  eifect  in  disturbing  or  altering  the  flame.  It  is  found  that 
Q  Minutes  of  Institution  of  Civil  Engineers,  vol.  i.,  p.  207. 


216 

the  wind  may  blow  suddenly  in  at  the  cowl,  and  the  effect  never 
reaches  the  lamp.  The  upper,  or  the  second,  or  the  third,  or  even 
the  fourth  portion  of  the  ventilating  flue  might  be  entirely  closed, 
yet  without  altering  the  flame.  The  cone  junctions  in  no  way  inter- 
fere with  the  tube  in  carrying  up  all  the  products  of  combustion;  but 
if  any  downward  current  occurs,  they  dispose  of  the  whole  of  it  into 
the  room  without  ever  affecting  the  lamp.  The  ventilating  flue  is  in 
fact  a  tube,  which,  as  regards  the  lamp,  can  carry  everything  up  but 
conveys  nothing  doivn." 

The  advantages  of  this  arrangement,  as  applied  to  the  Northern 
light-houses,  were  much  less  palpable  than  those  which  are  described 
in  the  beginning  of  Dr.  Faraday's  paper,  because  their  ventilation 
was  very  good  before  its  introduction;  and  the  flame  in  particular 
was  perfectly  steady,  being  by  no  means  subject  to  derangement 
from  sudden  gusts  of  wind  from  the  roof  in  the  manner  noticed 
above. 

All  the  light-houses  in  the  district  of  the  Scotch  Commissioners 
are  under  the  charge  of  at  least  two  light-keepers,  whose  duties  are 
to  cleanse  and  prepare  the  apparatus  for  the  night  illumination,  to 
mount  guard  singly  after  the  light  is  exhibited,  and  to  relieve  each 
other  at  stated  hours,  fixed  by  the  printed  regulations  and  instruc- 
tions under  which  they  act.  The  rule  is,  that  no  keeper  on  watch 
shall,  under  any  circumstances,  leave  the  light-room  until  relieved 
by  his  comrade;  and,  for  the  purpose  of  cutting  off  all  pretext  for 
the  neglect  of  this  universal  law,  the  dwelling-houses  are  built  close 
to  the  light-tower,  and  means  are  provided  for  making  signals  directly 
from  the  light-room  to  the  sleeping  apartments  below.  The  signals 
are  communicated  by  air  tubes  (Plate  XII)  which  pass  from  the 
light-room  to  the  sleeping  apartments  in  the  houses,  and  through 
which,  by  means  of  a  small  piston,  or  puff  of  wind  from  the  mouth, 
calls  can  be  exchanged  between  the  keepers.  The  man  on  guard  in 
the  light-room,  at  the  end  of  the  watch  or  on  any  sudden  emergency, 
may  thus  summon  his  comrade  from  below,  who,  on  being  thus 
called,  answers  by  a  counter-blast,  to  show  that  the  summons  has 
been  heard  and  will  be  obeyed.  For  the  purpose  of  greater  secu- 
rity, in  such  situations  as  the  Bell  Rock  and  the  Skerryvore,  four 
keepers  are  provided  for  one  light-room,  one  being  always  ashore  on 
leave  with  his  family,  and  the  other  three  being  at  the  light-house, 
so  that  in  case  of  the  illness  of  one  light-keeper  an  efficient  establish- 
ment of  two  keepers  for  watching  the  light  may  remain.  At  all  the 


217 

land  light-houses,  also,  an  agreement  is  made  with  some  steady  per- 
son residing  in  the  neighborhood,  who  is  instructed  in  the  manage- 
ment of  the  light  and  cleansing  of  the  apparatus,  and  comes  under 
an  obligation  to  do  duty  in  the  light-room  when  called  upon,  in  the 
event  of  the  sickness  or  absence  of  one  of  the  light-keepers.  This 
person  is  called  the  occasional  keeper,  and  receives  pay  only  while  ac- 
tually employed  at  the  light-house;  but  in  order  to  keep  him  in  the 
practice  of  the  duty,  he  is  required  to  serve  in  the  light-room  for  a 
fortnight  annually  in  the  month  of  January.  For  the  more  minute 
details  of  the  light-keepers'  duty,  I  would  refer  the  reader  to  the  in- 
structions already  alluded  to,  which  will  be  found  at  the  end  of  this 
volume. 

Each  of  the  two  light-keepers  has  a  house  for  himself  and  family, 
both  being  under  a  common  roof,  but  entering  by  separate  doors,  as 
shown  in  Plates  XI  and  XII,  which  exhibit  the  buildings  for  the 
new  light-house  at  Aduarmurchan  point,  on  the  coast  of  Argyleshire. 
The  principal  keeper's  house  consists  of  six  rooms,  two  of  which  are 
at  the  disposal  of  the  visiting  officers  of  the  board,  whose  duty  in  in- 
specting the  light-house  or  superintending  repairs  may  call  them  to 
the  station;  and  the  assistant  has  four  rooms,  one  of  which  is  used  as 
a  barrack-room  for  the  workmen  who,  under  the  direction  of  the 
foreman  of  the  light-room  works,  execute  the  annual  repairs  of  the 
apparatus. 

The  early  light-houses  contained  accommodation  for  the  light- 
keepers  in  the  tower  itself,  but  the  dust  caused  by  the  cleaning  of 
those  rooms  in  the  tower  was  found  to  be  very  injurious  to  the  deli- 
cate apparatus  and  machinery  in  the  light-room.  Unless,  therefore, 
in  situations  such  as  the  Eddystone,  the  Bell  Rock,  or  the  Skerry- 
vore,  where  it  is  unavoidable,  the  dwellings  of  the  light-keepers 
ought  not  to  be  placed  in  the  light-tower,  but  in  an  adjoining 
building. 

Great  care  should  be  bestowed  to  produce  the  utmost  cleanliness 
in  everything  connected  with  a  light-house,  the  optical  apparatus  of 
which  is  of  such  a  nature  as  to  suffer  materially  from  the  effect  of  dust 
in  injuring  its  polish.  For  this  purpose,  covered  ash-pits  are  provided 
at  all  the  dwelling-houses,  in  order  that  the  dust  of  the  fire-places 
may  not  be  carried  by  the  wind  to  the  light-room  ;  and,  for  similar 
reasons,  iron  floors  are  used  for  the  light-rooms  instead  of  stone, 
which  is  often  liable  to  abrasion,  and  all  the  stone  work  near  the 
lantern  is  regularly  painted  in  oil. 


218 

If,  in  all  that  belongs  to  a  light-house,  the  greatest  cleanliness  be 
desirable,  it  is  in  a  still  higher  degree  necessary  in  every  part  of  the 
light-room  apparatus,  without  which  the  optical  instruments  and  the 
machinery  will  neither  last  long  nor  work  well.  Every  part  of  the 
apparatus,  whether  lenses  or  reflectors,  should  be  carefully  freed  from 
dust  before  being  either  washed  or  burnished  ;  and  without  such  a 
precaution,  the  cleansing  process  would  only  serve  to  scratch  them. 
For  burnishing  the  reflectors,  prepared  rouge  (tritoxide  of  iron)  of  the 
finest  description,  which  should  be  in  the  state  of  an  impalpable 
powder  of  a  deep  orange-red  color,  is  applied,  by  means  of  soft 
chamois  skins,  as  occasion  may  require;  but  the  great  art  of  keeping 
reflectors  clean  consists  in  the  daily,  patient,  and  skilful  application 
of  manual  labor  in  rubbing  the  surface  of  the  instrument  with  a  per- 
fectly dry,  soft  and  clean  skin,  without  rouge.  The  form  of  the  hol- 
low paraboloid  is  such  that  some  practice  is  necessary  in  order  to 
acquire  a  free  movement  of  the  hand  in  rubbing  reflectors ;  and  its 
attainment  forms  one  of  the  principal  lessons  in  the  course  of  the 
preliminary  instruction  to  which  candidates  for  the  situation  of  a 
light-keeper  are  subjected  at  the  Bell  Rock  light-house.  For  cleans- 
ing the  lenses  and  glass  mirrors,  spirits  of  wine  is  used.  Having 
washed  the  surface  of  the  instrument  with  a  linen  cloth  steeped  in 
spirits  of  wine,  it  is  carefully  dried  with  a  soft  and  dry  linen  rubber, 
and  finally  rubbed  with  a  fine  chamois  skin,  free  from  any  dust  which 
would  injure  the  polish  of  the  glass,  as  well  as  from  grease.  It  is 
sometimes  necessary  to  use  a  little  fine  rouge  with  a  chamois  skin, 
for  restoring  any  deficiency  of  polish  which  may  occur  from  time  to 
time;  but  in  a  well  managed  light-house  this  application  will  seldom, 
if  ever,  be  required. 

The  machinery  of  all  kinds,  whether  that  of  the  mechanical  lamp 
or  the  revolving  apparatus,  should  also  be  kept  scrupulously  clean, 
and  all  the  journals  should  be  regularly  and  carefully  oiled.  *  * 

There  are  now  no  fewer  than  twenty-six  floating  lights  on  the  coast 
of  England. 

By  the  kindness  of  the  Elder  Brethren  of  the  Corporation  of  Trinity 
House  of  Deptford  Strond,  I  am  enabled  to  give  the  following  brief 
sketch  of  the  nature  and  peculiarities  of  floating  lights,  which  was 
communicated  to  me  by  Mr.  Herbert,  the  secretary  of  the  corpora- 
tion : 

' '  The  annual  expense  of  maintaining  a  floating  light,  including  the 
wages  and  victualing  of  the  crew,  who  are  eleven  in  number,  is  on 


219 

an  average  XI,  000 ;  and  the  first  cost  of  such  a  vessel,  fitted  complete 
with  lantern  and  lighting  apparatus,  anchors,  cables,  &c.,  is  nearly 
£5, 000.  The  lanterns  are  octagonal  in  form,  five  feet  six  inches  in 
diameter  ;  and,  where  fixed  lights  are  exhibited,  they  are  fitted  with 
eight  Argand  lamps,  each  in  the  focus  of  a  parabolic  reflector  of 
twelve  inches  diameter  ;  but,  in  the  revolving  lights,  four  lamps  and 
reflectors  only  are  fitted.  The  greatest  depth  of  water  in  which  any 
light-vessel  belonging  to  the  Corporation  of  Trinity  House  of  Dept- 
ford  Strond  at  present  rides,  is  about  forty  fathoms,  (which  is  at  the 
station  of  the  Seven  Stones  between  the  Scilly  islands  and  the  coast 
of  Cornwall. ) 

"The  corporation's  light- vessels  are  moored  with  chain-cables  of 
1-2  inch  diameter,  and  a  single  mushroom  anchor  of  32  cwt.,  in  which 
cases  the  chain-cables  are  200  fathoms  in  length  ;  some  of  said  vessels 
are  moored  to  span-ground  moorings,  consisting  of  100  fathoms  of 
chain  to  each  arm,  and  a  mushroom  anchor  of  similar  weight  at  the 
end  of  each  ;  a  riding  cable  of  150  fathoms  being  in  such  cases 
attached  to  the  centre  ring  of  the  ground  chain.  The  tonnage  and 
general  dimensions  of  the  light-vessels  are  given  on  the  drawing  of 
the  lines." 

Still  lower  in  the  scale  of  "signs  and  marks  of  the  sea,'*'  are  bea- 
cons and  buoys,  which  are  used  to  point  out  those  dangers  which, 
either  owing  to  the  difficulty  and  expense  that  would  attend  the 
placing  of  more  efficient  marks  to  serve  by  night  as  well  as  by  day, 
are  necessarily  left  without  lights,  or  which,  from  the  peculiarity  of 
their  position,  in  passages  too  intricate  for  navigation  by  night,  are, 
in  practice,  considered  to  be  sufficiently  indicated  by  day-marks  alone. 
Beacons,  as  being  more  permanent,  are  preferred  to  buoys  ;  but  they 
are  generally  placed  only  on  rocks  or  banks  which  are  dry  at  some 
periods  of  the  tide.  On  rocks,  in  exposed  situations,  beacons  are  some- 
times of  squared  masonry,  secured  by  numerous  joggles;  but,  in  situa- 
tions difficult  of  access,  and  in  which  works  of  uncompleted  masonry 
could  not  be  safely  left  during  the  winter  season,  an  open  frame-work 
of  cast-iron  pipes,  firmly  trussed  and  braced,  and  secured  to  the  rock 
with  strong  louis-bats,  is  preferred.  The  details  of  this  frame-work 
are  shown  at  plate  XIII.  A  stone  beacon,  of  about  forty  feet  high, 
may  be  erected  for  about  .£700,  and  an  iron  beacon  for  about  £640. 
In  less  exposed  places,  where  the  bottom  is  rock,  gravel,  or  hard 
sand,  a  conical  form  of  beacon,  composed  of  cast-iron  plates,  united 
with  flanges  and  screws,  with  rust  joints  between  them,  and  partially 


220 

filled  with  concrete,  is  sometimes  used.  A  beacon  of  that  kind  can 
be  erected  for  about  £400. 

Lastly,  buoys,  which  may  be  regarded  as  the  least  efficient  kind 
of  mark,  and  as  bearing  the  same  relation  to  a  beacon  that  a  float- 
ing light  does  to  a  light-house,  are  used  to  mark  by  day  dangers 
which  are  always  covered  even  at  low  water,  and  also  to  line  out  the 
fairways  of  channels.  They  are  of  three  kinds,  viz  :  the  nun-buoy, 
in  the  form  of  a  parabolic  spindle,  generally  truncated  at  one  end,  so 
as  to  carry  a  mast  or  frame  of  cage-work,  and  loaded  at  the  other 
end,  so  as  to  float  in  a  vertical  position  ;  the  can-buoy,  which  is  a 
conoid  floating  on  its  side  ;  and,  lastly,  the  cask-buoy,  which  is  a  short 
frustum  of  a  spindle  truncated  at  both  ends,  but  almost  exclusively 
used  for  carrying  the  warps  of  vessels  riding  at  moorings.  Those 
buoys  are  of  various  sizes  and  differ  in  cost.  Mast  buoys,  from  ten 
to  fifteen  feet  in  length,  cost  from  £'23  15s.  to  £48  ;  and  those  of  the 
Kibble  and  the  Tay,  which  are  twenty-one  and  twenty-four  feet  long, 
cost  respectively  £105  and  £79  ;  the  can-buoys  are  from  five  to  eight 
feet  long,  and  cost  from  £13  13s.  to  £20  5s.  Smaller  buoys  are  also 
used  in  narrow  estuaries  or  rivers.  Large  buoys  are  often  built  on 
kneed  frames,  resembling  the  timbers  of  vessels.  The  cask-buoy  is 
generally  six  feet  long,  and  costs  £22  15s.  All  those  buoys  are 
formed  of  strong  oaken  barrel-staves,  well  hooped  with  iron  rings, 
and  shielded  with  soft  timber  ;  and  the  nozzle-pieces  at  the  small  end 
of  the  nun  and  caw-buoys  are  generally  solid  quoins  of  oak  or  iron, 
formed  with  a  raglet  or  groove  to  receive  the  ends  of  the  staves. 
Much  skill  on  the  part  of  the  cooper  is  required  in  heating  and 
moulding  the  staves  to  the  required  form;  and  great  care  must  be 
taken  that  they  be  of  well-seasoned  timber.  Buoys  are  not  caulked 
with  oakum,  but  with  dry  flags,  which  are  closely  compressed  between 
the  edges  of  the  staves,  and  swell  on  being  wet ;  and  they  are  care- 
fully proved  by  steaming  them  like  barrels,  to  see  if  they  be  quite 
tight.  Sheet  iron  is  sometimes  used  in  making  buoys,  and  they  are 
then  sometimes  protected  with  fenders  of  timber;  but  they  have  been 
found  more  troublesome  for  transport,  and,  for  most  situations,  are 
considered  less  convenient  than  those  of  timber.  An  attempt  has 
lately  been  made,  under  my  direction,  to  construct  buoys  of  gutta 
percha,  stretched  on  a  frame  of  timber;  but  I  cannot  at  present  speak 
confidently  of  the  result. 

In  the  beginning  of  1845,  I  suggested  the  idea  of  rendering  beacons 
and  buoys  useful  during  night,  by  coating  them  with  some  phospho- 


221 


rescent  substance,  or  surmounting  them  with  a  globe  of  strong  glass 
filled  with  such  a  preparation,  whose  combustion  is  very  slow,  and 
emits  a  dull  whitish  light  and  little  heat.  Some  experiments  were 
accordingly  made;  but  no  practically  useful  result  has  been  obtained. 
In  laying  down  beacons  or  buoys,  their  position  is  fixed  either  by 
the  intersection  of  two  lines  draAvn  through  two  leading  objects  on 
the  shore,  (the  magnetic  bearings  of  which  are  given  for  the  sake  of 
easy  reference  on  the  spot,  in  finding  out  the  marks,)  or  by  means  of 
the  angles  contained  between  lines  drawn  to  various  objects  on  the 
shore,  which  meet  at  the  beacon  or  buoy  from  which  they  are  meas- 
ured by  means  of  a  sextant.  In  the  latter  case,  the  angles  are  always 
measured  around  the  whole  horizon,  thus  affording  a  check  by  the  dif- 
ference of  their  sum  from  360°.  The  magnetic  bearing  of  one  of  those 
lines  is  afterwards  carefully  ascertained  by  means  of  the  prismatic 
compass,  (if  possible  from  one  of  the  objects  on  shore,  and  if  not, 
conversely  from  the  beacon  or  buoy,)  so  as  to  afford  the  means  of 
translating  the  whole  into  magnetic  bearings  for  the  use  of  seamen. 
The  buoys  are  moored  by  means  of  chains  and  iron  sinkers,  with  a  suf- 
ficient allowance  in  the  length  of  the  chain  to  permit  them  to  ride 


[Extract  from  the  Journal  of  the  Franklin  Institute.] 

AN  ACCOUNT  OF  THE  CONSTRUCTION  OF  THE  NEW  LIGHT- 
HOUSE AT  THE  PORT  OF  HAVANA,  CUBA. 

By  Senor  Don  Jose  Benites,    Colonel  of  Royal  Engineers. 

[Translated  from  the  Spanish  for  the  Journal  of  tbe  Franklin  Institute  ] 

The  improvement  of  the  light  at  the  Moro  Castle,  which  serves  as 
a  guide  to  vessels  entering  the  port  of  Havana,  in  such  manner  as  to 
correspond  not  only  with  the  importance  of  its  commerce,  but  also 
with  the  perfection  to  which  the  construction  of  this  kind  of  appara- 
tus has  now  attained,  having  been  determined  upon  by  the  royal  junta 
of  protection,  the  department  of  the  marine  was  naturally  consulted 
with  regard  to  the  most  eligible  situation  and  the  proper  altitude  of 
the  new  light. 

That  illustrious  body  was  of  opinion  that  a  light  placed  at  the  same 
entrance  to  the  port  as  the  former  one  would  be  preferable  to  a  light 


222 

elsewhere,  although  it  might  be  situated  on  a  more  elevated  point  of 
the  coast,  owing  to  the  particular  configuration  of  which  it  might  be 
seen  from  further  to  the  windward.  With  regard  to  the  height,  it 
was  judged  sufficient  to  give  an  additional  elevation  of  twenty-five 
feet  to  the  old  tower,  because  the  light,  being  thus  placed  at  one 
hundred  and  forty-two  feet*  above  the  level  of  the  sea,  would  over- 
look the  point  called  Del  Pajonal,  which  bears  about  N.  71°  E.,  and 
might,  therefore,  be  readily  distinguished  and  recognized  by  vessels 
approaching  the  port  from  that  direction,  within  not  less  than  eight 
nor  more  than  fifteen  miles  of  the  coast,  and  affording  still  greater  ad- 
vantages to  those  standing  in  more  from  the  northward.  And,  more- 
over, that  with  the  proposed  elevation,  this  light-house  would  be  one 
of  the  highest  which  are  known. 

In  accordance  with  this  report,  the  junta  determined,  on  the  22d 
of  April,  1840,  to  proceed  with  the  execution  of  the  work  ;  and  its 
president,  the  most  excellent  Captain  General,  directed  that  the 
corps  of  engineers  should  make  the  proper  examination,  in  order  to 
ascertain  the  practicability  of  giving  to  the  old  tower  the  desired  ad- 
ditional elevation.  By  a  report  of  the  commandant,  June  2d,  1840, 
it  was  declared  practicable  to  add  the  proposed  twenty-five  feet  to 
the  height  of  the  tower,  provided  the  work  were  carefully  done,  and 
with  materials  of  the  best  kind. 

In  this  state  the  project  rested  until  the  16th  of  October,  1843, 
when  the  junta,  through  its  president,  asked  that  the  funds  necessary 
for  the  work  should  be  remitted,  inasmuch  as  it  would  also  be  neces- 
sary, in  addition  to  the  projected  increase  in  the  height  of  the  tower, 
to  order  from  Paris  a  lenticular  lantern  of  the  most  improved  kind, 
by  Fresnel,  to  be  placed  therein.  The  requisite  funds  having  been 
provided,  it  was  resolved,  on  the  7th  of  April,  1844,  to  proceed  with 
the  work,  but  with  the  indispensable  condition  that  the  light  should 
not  be  interrupted  for  a  single  night.  Accordingly,  the  construction 
of  a  small  temporary  tower  was  commenced  on  the  22d  of  May,  for  the 
purpose  of  sustaining  the  light  while  the  height  of  the  old  tower  was 
being  increased  by  additional  mason-work.  The  great  height  of  the 
platform  upon  which  the  temporary  tower  was  constructed,  rendered 
it  unnecessary  to  give  it  an  elevation  of  more  than  seven  yards  in 
order  to  maintain  the  light  at  the  same  height  as  that  at  which  it  was 
placed  in  the  old  tower.  Its  immediate  proximity  to  this,  and  the 
removal  of  the  light  to  the  temporary  tower  in  a  single  day,  rendered 

~-  The  Spanish  foot  here  used  is  equal  to  11.1  inches,  and  the  vara,  or  yard,  is  33.3  inches. 


it  unnecessary  to  give  that  notice  in  the  public  papers  which  would 
otherwise  have  been  requisite  in  order  to  avoid  dangerous  conse- 
quences to  vessels.  On  the  23d  of  July,  1844,  the  temporary  light- 
house was  first  put  into  use;  its  cost,  including  the  lantern,  amounting 
to  the  sum  of  $1, 800.  Its  strength,  and  the  judicious  principles  upon 
which  it  was  constructed,  were  fully  proved  in  the  terrible  hurricane 
of  the  5th  of  October  last ;  during  which,  though  exposed,  without 
the  least  protection  from  other  buildings,  to  the  force  of  the  wind 
and  the  beating  of  the  waves,  it  remained  firm,  and  without  other 
injury  than  a  total  destruction  of  the  glass  in  the  lantern. 

The  next  step  was  the  taking  down  of  the  lantern  from  the  old 
tower,  and  to  proceed  with  other  preparations  for  increasing  its 
height,  when,  on  the  14th  of  August,  1844,  notice  was  received  by 
the  board  of  engineers,  from  his  excellency,  the  Captain  General, 
that,  by  a  resolution  of  the  junta,  adopted  in  virtue  of  a  report  from 
their  commissioners,  it  was  determined  to  suspend  the  work,  and 
inquire  whether  it  would  not  be  more  expedient,  provided  the  funds 
were  sufficient,  to  construct  a  tower  upon  a  new  plan,  which  should 
combine  all  the  beauty,  convenience,  and  facility  which  would  bo 
required  for  the  proper  management  of  an  apparatus  so  complicated 
as  that  of  Fresnel ;  advantages  which  could  not  be  afforded  by  the 
old  tower  on  account  of  its  limited  dimensions,  and  its  total  want  of 
accommodations  for  the  persons  entrusted  with  the  care  of  the  light 
during  the  night,  as  well  as  its  narrow  and  inconvenient  stairway. 
The  board  of  engineers,  as  was  to  be  expected,  reported  in  favor  of 
the  new  project,  and  at  the  same  time  submitted  a  plan  and  an  esti- 
mate for  the  new  tower.  Both  of  these  were  approved  by  the  junta 
at  its  session  on  the  16th  of  August,  and  the  work  was  ordered  to  be 
carried  into  effect.  On  the  following  day  the  demolition  of  the  old 
tower  was  commenced,  and,  at  the  same  time,  the  excavation  of  a 
foundation  for  the  new  one  was  begun,  in  order  that  the  old  materials 
might  be  used  in  it. 

Situation  of  the  nciv  tower. — Of  the  rock  upon  which  the  Moro  cas- 
tle is  built,  that  point  which  extends  farthest  towards  the  N.  W., 
and  on  which  the  old  tower  stood,  is  divided  from  the  rest  by  a  cleft 
or  fissure,  and  is  also  undermined  by  a  large  cavern,  washed  out  by 
the  continual  beating  of  the  waves.  In  order  to  avoid  these  defects, 
which  might,  in  time,  endanger  the  stability  of  the  new  edifice,  and 
also  because  the  space  afforded,  for  the  ground  plan  was  not  sufficient, 
a  place  was  chosen  eighty-four  feet  farther  back  than  the  position 


224 

occupied  by  the  old  tower,  and  on  the  broadest  part  of  the  glacis  of 
the  Morillo — a  position  combining  all  the  advantages  of  the  former 
one,  besides  leaving  free  the  extreme  point  of  the  Morillo — for  the 
erection  of  a  battery  of  three  Paixhan  guns,  of  large  calibre,  in  such 
a  very  advantageous  position.  Care  was  also  taken  to  leave  sufficient 
space  about  the  new  tower  for  the  free  use  and  management  of  the 
cannon  which  defend  the  entrance  to  the  port,  as  well  as  of  those  on 
the  opposite  side. 

Description  of  the  tower. — It  is  composed  of  two  parts  ;  the  first 
representing  a  column  seventy-nine  feet  high,  twenty-five  feet  in 
diameter  at  the  base,  and  twenty  at  the  top.  The  cornice  of  this 
serves  as  the  floor  of  a  corridor  with  a  circular  parapet,  enclosed  by 
a  grated  railing  of  copper,  which  surrounds  the  upper,  or  second 
part,  upon  which  the  lantern  is  supported.  The  first  or  lower  part 
is  constructed  of  hewn  stone,  the  wall  being  seven  feet  thick  at  the 
base,  vertical  in  the  interior,  and  sloping  on  the  outside,  thirty  inches 
in  the  whole  height.  The  interior  space  of  eleven  feet  in  diameter 
serves  for  a  circular  staircase,  the  steps  of  which  are  four  feet  long, 
seven  and  a  half  inches  high,  nineteen  inches  broad  at  the  wide  end, 
and  six  at  the  other,  or  immediately  at  the  spindle  or  central  column 
of  three  feet  in  diameter,  which  extends  up  through  the  whole  height. 
The  stairway  begins  inside,  at  thirty-eight  inches  in  the  clear  from 
the  door,  in  order  to  leave  an  open  landing  place  ;  the  steps  being 
covered  with  slabs  of  marble  one  and  a  half  inch  in  thickness,  with 
a  moulding  which  extends  an  inch  beyond  the  step.  The  doorway 
in  the  lower  part  of  the  tower,  which  gives  entrance  to  the  stairway, 
is  four  feet  wide  and  eight  feet  high,  with  pilasters  at  the  sides,  and 
its  cornice  and  frontispiece  in  the  form  of  a  circular  arch.  Over  the 
door  is  a  block  of  marble  containing  an  inscription  in  Spanish  of  the 
following  purport  : 

In  the  year  1844  : 

Isabella  the  Second  reigning ; 

The  Junta  of  Protection  under  the  Presidency  of 

the  Captain  General  of  the  Island,  Don  Leopold  O'Donncll  ; 

This  work  was  executed  under  the  direction  of 

the  Corps  of  Engineers  of  the  Army. 

The  stairway  is  lighted  and  ventilated  by  three  i  ets  of  windows, 
placed  equi-distant  from  one  another  throughout  the  whole  height. 
They  are  four  feet  high  and  two  feet  wide,  and  in  six  of  them  the 
lower  part  of  the  niche,  or  recess  in  the  wall  which  forms  the  win- 


225 

dow,  is  level  with  the  steps,  and  serves  as  a  landing  or  resting  place. 
BeloAV  the  stairway,  and  at  the  level  of  the  lower  floor  of  the  tower, 
is  a  spacious  room,  enclosed  by  a  wooden  railing,  which  is  used  as  a 
place  of  deposit  for  oil  and  the  more  heavy  and  bulky  articles  used 
about  the  light-house. 

At  the  height  of  sixty-three  feet  nine  inches  the  stairway,  which 
has  been  described,  terminates  in  an  apartment  called  the  attendant's 
room,  twelve  feet  in  diameter  and  twelve  and  a  half  in  height,  cov- 
ered by  an  arch  two  feet  in  the  crown.  This  chamber,  lined  with 
marble,  is  intended  for  the  two  persons  who  have  charge  of  the  light 
during  the  night.  It  is  furnished  with  windows,  and  the  requisite 
conveniences  for  containing  a  supply  of  lamps,  funnels,  wicks,  oil, 
<fcc.,  <fcc.,  having  a  staircase  of  mahogany,  with  a  balustrade  attached 
to  the  wall.  The  breadth  of  this  stairway  is  twenty-four  inches  ;  the 
steps  are  a  foot  high  and  eight  inches  broad  in  the  middle  ;  it  leads, 
through  an  opening  left  in  the  arch  to  the  platform,  or  upper  part 
of  the  lower  edifice. 

Upon  this  platform  is  erected  a  second  structure,  consisting  of  a 
circular  wall  of  hewn  stone,  two  and  a  half  feet  thick,  eight  feet 
high,  and  eleven  feet  seven  inches  in  its  interior  diameter.  The 
latter  dimensions  are  determined  by  the  base  and  diameter  of  the 
lantern,  which,  as  has  been  before  said,  rests  upon  it.  In  this  second 
part  of  the  tower  there  is  a  door  six  feet  high  by  twenty-seven  inches 
wide,  to  admit  of  egress  to  the  platform,  or  corridor,  above  the  cor- 
nice. In  the  floor  of  the  apartment  within  the  upper  edifice,  which 
is  called  the  lantern  room,  and  which  is  also  lined  with  marble,  there 
are  two  apertures  ;  one  in  the  centre,  which  is  circular  and  twelve 
inches  in  diameter,  into  which  is  introduced  the  foot  or  support  of 
the  apparatus;  the  other  is  a  foot  and  a  half  long  by  two  inches  wide, 
for  the  passage  of  the  cord  to  which  the  moving  weight  is  suspended. 
This  weight  is  raised  by  means  of  a  pulley  placed  in  the  arched  ceil- 
ing of  the  attendants'  room,  and  is  enclosed  in  a  case  thirteen  inches 
square  and  twelve  yards  long,  formedym  the  thickness  of  the  wall  of 
the  lower  part  of  the  tower. 

The  total  height  of  the  tower  is,  therefore,  eighty. seven  feet; 
which,  added  to  the  elevation  of  its  base  above  the  level  of  the  sea, 
sixty-five  and  a  half  feet,  and  to  the  height  of  the  light  within  the 
lantern,  five  and  a  half  feet,  will  make  the  total  elevation  of  the 
light  one  hundred  and  fifty-eight  feet,  the  horizontal  tangent  of 
which  is  thirteen  and  a  half  marine  miles.  This  exceeds,  by  sixteen 
15 


226 

feet,  the  height  desired  in  the  marine  department,  and  the  light  is 
consequently  visible  about  a  mile  further  than  the  distance  required 
by  them. 

Description  of  the  apparatus  for  lighting. — In  order  to  give  a  clear 
and  connected  idea  of  this,  we  shall  omit  a  detailed  account  of  the 
numerous  parts  of  which  the  various  portions  of  this  complicated 
machinery  consist,  and  shall  proceed  to  describe  only  such  of  them 
as  will  serve  to  make  the  mechanism  understood,  even  by  those  who 
are  not  entirely  familiar  with  the  mechanical  and  optical  principles 
upon  which  it  is  constructed. 

The  new  apparatus  for  lighting  consists  of  four  distinct  parts,  as 
follow : 

1.  The  mechanical  lamp. 

2.  The  system  of  prismatic  lenses  and  reflectors  placed  around  the 
light. 

3.  The  machine  \vhich  gives  a  uniform  rotary  movement  to  the 
prismatic  lenses. 

4.  The  glass  lantern  which  covers  the  whole  without  obscuring  the 
light. 

The  mechanical  lamp. — This  lamp,  placed  in  the  centre  of  the 
lenses  and  reflectors,  is  supported  by  a  hollow  pillar  of  bronze,  seven 
feet  two  inches  high,  having,  below,  a  receptacle  for  the  oil,  and  a 
set  of  pumps  for  raising  it.  These  pumps  are  worked  by  machinery 
similar  to  that  of  a  clock,  the  moving  weight  being  contained  within 
the  pillar,  and  are  capable  of  raising  four  times  the  quantity  of  oil 
which  the  burners  require;  from  which  it  follows  not  only  that  the 
flame  is  maintained  with  all  possible  brilliancy,  but  also  that  the 
superfluous  oil  which  flows  over  the  exterior  surface  of  the  tubes 
and  falls  back  into  the  cistern,  cools  the  points  of  the  tubes,  which 
might  otherwise  be  fused  by  the  intensity  of  the  heat.  In  order  to 
increase  the  watchfulness  of  those  who  have  the  care  of  the  light  it 
is  furnished  with  alarm  bells.  The  escapement  of  this  machinery  is 
connected  with  one  end  of  a  lever,  and  at  the  other  is  suspended  a 
vase  with  a  small  hole  in  the  bottom.  This  vessel  is  so  placed  as  to 
receive  the  superfluous  oil  from  the  burners,  and,  while  full,  it  sus- 
tains the  counterpoise,  but  as  soon  as  it  begins  to  vary  on  account  of 
a  deficiency  of  oil,  the  lever  loosens  the  movement  of  the  alarm  ap- 
paratus, which  gives  notice  of  the  irregularity.  A  first  class  light 
has  three  lamps,  so  that  if  one  of  them  shall  be  out  of  order,  there 
are  still  two  fit  for  use,  in  good  condition,  and  the  light  is  constantly 
maintained.  The  Havana  light  has  four. 


227 

The  prismatic  lenses  and  reflecting  mirrors. — The  lenses  and  reflect- 
ors, the  object  of  which  is  to  concentrate  the  rays  of  light  which 
proceed  from  the  burners  of  the  lamp,  in  order  to  give  them  a 
horizontal  direction,  are  placed  in  a  metallic  frame  conveniently 
arranged,  and  which,  as  well  as  the  lamp,  rests  upon  the  capital  of 
the  bronze  column.  One  part  of  this  frame,  which  contains  the  re- 
flectors, is  stationary,  while  the  other,  containing  the  prismatic 
lenses,  revolves  around  the  lamp  with  a  uniform  motion.  This  revo- 
lution of  the  lenses  causes  eclipses  of  the  light,  according  to  the  dif- 
ferent positions  which  they  successively  occupy  around  the  burner, 
producing  a  more  intense  and  lively  brilliancy/wi  the  direction  to- 
Avards  which  the  focus  of  each  lens  happens  to/#e  directed,  continuing 
thirty  seconds  before  it  is  replaced  by  the i/riext;  though,  on  account 
of  the  stationary  portion  of  the  apparatus  which  contains  the  reflect- 
ors, there  is  always  afforded,  in  all  directions,  a  less  brilliant  light, 
but  one  which  is  still  sufficient  to  enable  the  light-house  to  be  kept 
in  sight. 

The  machinery  which  gives  motion  to  the  prismatic  lenses. — The 
mechanism  of  this  is  like  that  of  a  clock,  and  is  placed  at  the  side  of 
the  bronze  pillar  which  supports  the  lamp,  A  pinion-wheel,  gearing 
into  another  connected  with  the  movable  portion  of  the  apparatus, 
puts  it  in  motion  by  the  action  of  a  weight  suspended  to  a  cord  pass- 
ing through  the  floor  of  the  room  which  contains  the  machinery,  and 
descending  below  into  a  case  made  in  the  wall  of  the  tower. 

The  lantern. — The  glass  lantern  which  encloses  the  light  rests  upon 
the  circular  wall  built  above  the  cornice  of  the  tower,  and  has  the 
figure  of  a  prism  of  sixteen  sides.  It  is  covered  by  a  cupola  of  cop- 
per, with  a  chimney  in  its  top  to  carry  oft*  the  gases  proceeding  from 
the  combustion;  the  whole  being  surmounted  by  a  weathercock. 

By  the  foregoing  description,  it  will  be  perceived  that  this  light- 
house, when  illuminated,  presents  constantly  a  steady  light,  uni- 
formly alternating,  every  six  seconds,  with  brilliant  flashes,  by  which 
it  may  be  distinguished  from  any  other  light. 

The  intensity  of  the  steady  light  is  equal  to  that  given  by  five 
hundred  and  fifty  burners  like  those  of  the  ordinary  Carcel  lamp, 
which  consume  three  and  a  quarter  ounces  of  oil  per  hour,  and  it 
may  be  easily  seen  at  a  distance  of  six  or  seven  marine  leagues. 
The  brightness  of  the  flashes  is  nearly  four  times  as  great  as  that  of 
the  steady  light,  and  equal  to  that  given  by  two  thousand  of  the 
abovementioned  Carcel  burners. 


228 

Data  for  determining  the  proper  thickness  for  the  icall  of  the  tower. — 
The  most  interesting  and  nice  question  which  first  presents  itself,  in 
considering  the  construction  of  a  very  high  tower,  is  to  determine 
the  thickness  which  its  walls  ought  to  have  in  order  to  insure  the 
necessary  stability,  and  to  resist  successfully  the  forces  which  have 
a  tendency  to  destroy  it.  This  is  a  general  principle  in  all  kinds  of 
edifices;  but  in  high  towers,  the  base  of  which  bears  a  small  propor- 
tion to  their  height,  it  is  necessary  to  consider  another  element  of 
destruction  more  powerful  and  active  than  the  force  of  gravitation, 
namely,  the  violence  of  the  wind  in  those  great  hurricanes  which  are 
so  frequent  on  seacoasts,  particularly  among  the  Antilles. 

In  the  calculation  of  this  force,  as  in  all  physico-mathematical 
questions,  the  data  are,  for  the  most  part,  derived  from  experiments, 
of  the  accuracy  of  which  we  cannot  be  precisely  certain,  but  which 
have  been  found  sufficiently  worthy  of  confidence  when  applied  to 
similar  structures  which  have  for  many  years  resisted  every  kind  of 
force;  and  in  this  case  there  is  nothing  more  logical  or  natural,  than 
to  take  the  result  of  these  calculations  as  the  established  data  of 
comparison  with  reference  to  our  own  case. 

The  data  upon  which  we  should  reckon  in  calculations  of  this  kind, 
founded  upon  numerous  experiments,  are  as  follows:  First,  the  pres- 
sure upon  a  superficial  metre,  when  the  wind  has  a  velocity  of  fifty 
metres  per  second,  which  is  that  of  the  greatest  hurricanes,  is  equal 
to  the  weight  of  two  hundred  and  seventy-five  kilogrammes,  or  about 
three  hundred  and  eighty-six  pounds  to  the  square  yard;  second,  the 
action  of  the  wind  upon  a  vertical  cylinder  is  reduced  to  two-thirds 
of  the  force  which  it  exerts  upon  a  central  vertical  section  of  the 
same  cylinder. 

To  apply  these  rules  to  the  stability  of  a  tower  composed  of  a  sin- 
gle stone  in  the  form  of  a  right  prism  with  a  square  base,  we  should 
multiply  the  superficial  area  of  one  of  its  sides  by  three  hundred 
and  eighty-six  pounds;  and  this  product  being  multiplied  by  half  the 
height  of  the  prism,  will  give  the  momentum  of  the  wind's  force. 
In  order  to  determine  the  momentum  of  resistance,  the  total  weight 
of  the  tower  should  be  multiplied  by  half  the  width  of  its  base.  Di- 
viding this  product  by  the  first  obtained  momentum  of  the  wind,  we 
have  the  expression  of  the  absolute  stability  of  the  edifice  with  regard 
to  the  action  of  hurricanes. 

Towers  are  composed  of  numerous  courses  of  cut  stone,  the  adhe- 
sion of  which  affects,  the  stability  in  proportion  to  the  decrease  in 


229 

the  size  of  the  blocks  of  stone  used.  If  we  suppose  this  adhesion  to 
be  nothing  in  a  wall  composed  of  courses  of  stretchers  and  ties,  the 
fracture  caused  by  the  force  of  the  wind  will  not  be  horizontal;  but  (as 
in  retaining  walls)  according  to  an  oblique  section,  the  inclination  of 
which  is  determined  by  the  maximum  of  relation  between  the  force  of 
the  wind  and  the  momentum  of  weight  of  the  solid  above  the  section. 
But  it  should  be  observed  that  in  most  high  towers,  the  adhesion  of 
the  cement  and  the  arrangement  of  the  materials  is  such  that  the 
section  of  rupture  is  less  inclined  than  in  ordinary  containing  walls, 
and  if,  in  addition  to  this,  we  also  consider  that  the  results  which  we 
seek  are  of  comparison  between  our  tower  and  those  whose  stability 
has  been  already  tested  by  having  for  a  long  time  resisted,  without 
injury,  every  kind  of  force,  the  supposition  that  the  section  of  frac- 
ture would  be  horizontal  should  have  no  sensible  influence. 

The  determination  of  the  section  of  most  easy  fracture  offers  a 
problem  of  minimums,  the  direct  solution  of  which,  in  general,  re- 
quires very  tedious  calculations;  but  fortunately  the  position  of  that 
section  is  apparent,  in  most  cases,  at  the  first  glance  of  the  eye,  or 
may  readily  be  determined  by  a  few  trials. 

In  case  the  tower  should  have  the  form  of  a  truncated  cone,  like 
that  of  which  we  are  treating,  if  it  should  ever  yield  to  the  force  of 
the  wind,  it  would  be  twisted  off  above  the  offset  of  its  base,  in  the 
direction  opposite  to  that  from  which  it  receives  the  force,  and  its 
being  broken  above  the  offset  would  be  because  the  arm  of  the  lever 
of  resistance,  instead  of  being  equal  to  the  radius  of  the  section  of 
rupture,  is  somewhat  less. 

These  principles  being  established,  it  is  known  that,  in  order  to 
give  great  stability  to  a  circular  wall  in  ordinary  structures,  it  is  suffi- 
cient to  make  the  thickness  a  twelfth  part  of  the  height;  consequently, 
having  to  raise  our  tower  to  a  height  of  eighty  feet,  a  thickness  of 
seven  feet  was  enough  for  the  wall;  but  as  the  tower  is  not  an  insu- 
lated wall,  but  has  within  it,  a  circular  stairway  which  binds  and 
fastens  together  all  its  parts,  and,  moreover,  as  the  consideration  of  a 
convenient  situation  for  the  illuminating  apparatus  required  that  the 
upper  part  of  the  tower  should  be  only  twenty  feet  in  diameter,  we 
were  able  to  start  with  seven  feet  at  the  base,  and  to  diminish  gradu- 
ally to  four  and  a  half  at  the  top,  with  the  advantage  of  an  exterior 
slope  of  two  and  a  half  feet  in  the  whole  height,  which  also  adds  to 
its  strength. 

Having  established  these  data,  it  now  remains  to  examine  whether, 


230 

with  these  dimensions,  the  tower  possesses  as  much,  or  greater, 
strength  than  others  similar  to  it,  which  have  been  built  many  years, 
and  have  resisted,  without  the  least  damage,  the  force  of  the  greatest 
storms,  and  I  say  it  ought  to  be  stronger:  1st,  Because  the  terms  of 
comparison  which  we  seek  are  derived  from  the  towers  built  in  Eu- 
rope, where  hurricanes  are  neither  so  frequent  nor  of  such  long  du- 
ration as  in  the  Antilles;  and,  2d,  Because  the  tower  which  we  have 
constructed,  from  its  peculiar  situation,  has  to  sustain  not  only  the 
force  of  the  wind  but  the  shock  of  the  waves,  although  this  is  some- 
what diminished  by  the  tower  being  placed  twenty-two  yards  above 
the  level  of  the  sea. 

For  comparison,  we  will  take  the  signal  tower  erected  in  1715,  at 
the  port  of  L' Orient,  the  form  of  which  is  similar,  on  the  whole,  to 
that  constructed  at  the  Moro,  and  which  has  withstood  until  the  pres- 
ent time,  without  injury,  all  the  force  of  the  storms. 

Stability  of  the  totver  at  L'  Orient. — The  result  of  a  calculation  with 
regard  to  this  tower  shows  that  the  relation  of  the  resistance  to  the 
pressure  is  7.4;  that  is  to  say,  the  resistance  is  7.4  times  greater  than 
the  pressure.  Let  us  now  see  what  result  will  be  obtained  by  an 
analogous  calculation  with  regard  to  the  tower  at  the  Moro. 

Calculation  of  the  stability  of  the  tower  at  the  Moro. — The  contents  of 
the  truncated  cone  which  constitutes  the  lower  part,  is  31,174  cubic 
feet.  The  interior  cylinder,  which  contains  the  staircase,  is  11  feet 
in  diameter  and  34£  in  circumference;  the  area  of  its  base,  95  square 
feet;  and  its  contents  95  X  78  —  7,410  cubic  feet.  Taking  this  from 
the  total  solid  contents,  there  remain  23,764  cubic  feet  for  the  solid 
contents  of  the  circular  wall  of  the  lower  part  of  the  tower.  The 
cylindrical  column  in  the  centre  of  the  circular  stairway  contains  450 
cubic  feet,  and  the  stairway  itself  306;  so  that  the  total  solidity  of 
the  masonry  in  the  lower  body  of  the  tower  is  24,520  cubic  feet,  or 
908  cubic  yards.  Adding  to  this  three  cubic  yards  for  the  projection 
of  the  cornice,  and  subtracting  thirty-six  yards  for  the  apertures  left 
for  doors  and  windows,  there  remain  875  cubic  yards  of  masonry. 
As  the  attendant's  room,  in  the  lower  section  of  the  tower,  is  a  foot 
larger  in  diameter  than  the  interior  space  occupied  by  the  stairway, 
it  follows  that  the  amount  of  masonry,  which  on  this  account  has 
been  rather  over-estimated,  will  >e  made  up  by  the  arched  ceiling  of 
this  room,  which  has  not  been  taken  into  the  account. 

The  solid  contents  of  the  circular  wall  which  forms  the  upper  sec- 
tion of  the  tower,  upon  which  the  lantern  is  placed,  is  twenty-seven 


231 

cubic  yards,  deducting  the  opening  for  the  door;  so  that  the  whole 
amount  of  solid  masonry  is  902  cubic  yards. 

A  cubic  yard  of  the  masonry  used  in  this  tower  weighs  eighty-five 
arrobas,  (twenty-five  pounds  each,)  and  the  arm  of  the  lever  of  resist- 
ance being  four  yards,  (a  little  less  than  the  radius  of  the  base,)  it  fol- 
lows that  the  power  of  the  resistance  will  be  902  X  4  X  85  =  306, 680. 

A  central  perpendicular  section  of  the  lower  portion  of  the  tower 
contains  195  square  yards:  of  the  upper  portion,  13;  and  of  the  lan- 
tern, 26,  presenting  a  total  sectional  superfice  of  234  square  yards. 
The  centre  of  gravity  of  these  three  superfices  is  found  at  thirteen 
3'ards  from  the  base  of  the  tower;  consequently  the  momentum  of 
pressure  from  the  wind  is  f  386  x  234  X  13=31,504  arrobas,  and  the 

ratio  of  the  resistance  to  the  pressures  3j)6'680— 9.7. 

31,504 

By  this  result  it  will  be  seen  that  the  tower  at  the  Moro  has  a 
stability  equal  to  nearly  one  and  a  half  times  that  of  the  tower  at 
L' Orient,  which  was  taken  for  comparison,  and  consequently  that  its 
dimensions  are  sufficient,  although  indispensable  for  the  reasons 
already  mentioned,  to  warrant  the  undertaking  of  its  construction 
with  entire  confidence. 

Details  of  the  construction.  Foundation. — As  the  tower  is  twenty- 
five  feet  in  diameter  at  its  base,  a  circle  28^  feet  in  diameter  was 
traced  around  the  centre  of  the  area  to  be  occupied  by  it  so  that 
the  excavation  for  the  foundation  being  larger  than  the  body  of  the 
tower,  a  berm  or  offset  of  twenty-one  inches  would  be  left  by  the 
extension  of  the  foundation  wall  beyond  that  of  the  tower  itself. 
The  excavation  was  carried  through  the  surface  soil  down  to  the 
rock  which  underlies  the  glacis  of  the  Morillo,  which  was  reached 
and  laid  bare  at  an  average  depth  of  fifteen  feet. 

The  rock  presented  an  irregular  surface,  in  consequence  of  which, 
together  with  its  extreme  hardness,  the  operation  of  cutting  it 
down  to  a  level  would  have  been  very  expensive.  It  was  therefore 
deemed  preferable  to  construct  the  foundation  by  steps,  (enescaiones,) 
using  blocks  of  stone  of  the  best  kind,  disposed  in  circular  horizontal 
layers,  (formando  anillos  en  capos  Jiorizontales,)  properly  placed,  and 
the  joints  filled  with  a  mixture  of  lime  and  sand  ;  taking  care,  as  in 
all  masonry  of  hewn  stone,  that  the  joints  of  each  layer  should  be 
covered  by  the  course  immediately  above  it. 

The  foundation  is  nine  and  a  half  yards  in  diameter  by  five  in 
depth,  and  consequently  contains  three  hundred  and  fifty-five  cubic 


232 

yards  of  masonry.  The  cost  of  its  excavation  and  refilling  was 
$1,554,  being  $4.375  per  cubic  yard.  In  the  calculation  of  the 
original  estimate  it  was  assumed  that  the  foundation  would  be  only 
three  yards  in  depth ;  consequently  containing  two  hundred  and 
thirteen  cubic  yards,  of  which  the  cost,  estimated  at  $7.50  per  yard 
for  the  masonry,  including  the  excavation,  amounted  to  $1,597.50, 
being  an  excess  of  $43.50. 

In  calculating  this  estimate  of  $7.50  per  cubic  yard  of  masonry,  it 
was  proposed  to  use  all  the  materials  of  the  old  tower  :  but  as  this 
would  not  be  sufficient,  it  was  supposed  that  the  stone  still  to  be 
provided  would  have  to  be  purchased  and  transported  from  the 
opposite  shore.  The  great  reduction  which  was  made  in  the  cost 
per  cubic  yard  of  this  work,  from  that  originally  estimated,  was 
owing  to  the  following  causes  :  First.  Instead  of  buying  from  in- 
dividuals the  stone  which  were  required,  those  were  procured  which 
remained  unused  from  the  erection  of  the  fortifications  at  that  place, 
and  which  has  been  taken  from  quarries  opened  for  that  purpose  ;  on 
which  account  they  were  obtained  at  a  much  lower  price,  while, 
at  the  same  time,  the  expensive  transportation  in  vessels  was  avoided. 
Second.  Because  it  was  not  necessary  to  purchase  sand  for  making 
the  cement,  having  used  that  which  was  found  in  the  fosses  of  the 
fortifications. 

The  digging  of  the  foundation  was  commenced  on  the  17th  of 
August,  1844,  and  by  the  24th  of  September  it  was  completed 
and  leveled  off  to  nine  inches  below  the  glacis  of  the  castle  ;  being 
then  in  order  for  receiving  the  first  layer  of  stone  for  the  tower. 
Daring  the  same  time  the  old  tower  was  completely  taken  down,  its 
materials,  as  has  been  already  said,  being  used  for  the  new  foun- 
dation. 

The  lower  part  of  the  tower. — Upon  the  level  top  of  the  basement, 
or  foundation,  the  first  layer  of  stone  forms  a  solid  floor  over  the 
whole  twenty-five  feet  in  diameter ;  its  outer  boarder  being  vertical 
and  forming  a  projection  or  socle  of  nine  inches  around  the  tower, 
as  well  as  a  step,  of  the  same  height,  for  entrance  into  it.  The 
building  is  then  continued  to  the  requisite  elevation  by  successive 
courses  of  eighteen  inches  in  height.  In  order  to  give  an  exterior 
slope  to  the  wall,  and  consequently  to  diminish  its  thickness  in  due 
proportion,  the  width  of  the  blocks  in  the  interior  courses  was 
gradually  contracted,  while  those  on  the  exterior  were  of  the  same 
breadth,  so  that  the  vertical  joints  might  recede  gradually  to- 


233 

wards  the  interior,  and  the  masonry  be  well  united  together ;  thus 
avoiding  the  defect  which  would  result  from  an  equal  diminution  in 
the  breadth  of  the  blocks  used  in  both  the  inner  and  outer  faces  of 
the  wall,  in  which  case,  the  vertical  joints  of  each  course  would  con- 
tinue to  be  one  above  another,  thus  forming  two  distinct  walls,  with- 
out further  connexion  than  that  of  the  extending  ties. 

The  circular  stairway  is  composed  of  entire  blocks  of  stone,  which 
are  inserted  six  inches  into  the  Avail,  each  of  them  forming  two  steps, 
together  with  the  corresponding  part  of  the  central  column,  or  nave,  of 
the  staircase.  It  was  carried  up  at  the  same  time  with  the  wall  of  the 
tower,  in  order  to  insure  the  proper  connexion  and  binding  together 
of  the  work,  and  also  served  for  use  during  the  construction  of  the 
building  ;  the  order  of  proceeding  being  first  to  set  the  block  of  stone 
which  formed  two  steps,  and  then  to  lay  the  corresponding  course 
on  the  wall,  and  so  on  successively.  The  nave,  or  central  part  of 
the  stairway,  is  cylindrical  throughout  its  whole  height,  except  at 
the  top,  where  it  increases  in  diameter,  with  a  view  of  gaining  a 
certain  space  on  the  floor  of  the  attendants'  room.  In  order  to  give 
this  proper  form  to  the  central  column,  its  diameter  was  gradually  en- 
larged, beginning  at  the  seventeenth  step  from  the  top,  and  so  con- 
tinuing to  the  last ;  so  that  the  stairway  is  only  twenty-seven  inches 
wide  in  the  last  six  feet  of  its  flight. 

The  upper  part  of  the  tower. — This  is  a  simple  circular  wall  of  cut 
stone,  composed  of  blocks  in  alternate  order,  and  presenting  nothing 
worthy  of  special  notice. 

Arch  of  the  attendants'  room. — This  arch  is  in  the  form  of  a  simple 
dome,  and  presents  nothing  remarkable  in  its  construction.  The 
thickness  of  the  wall  which  supports  it  is  that  which  is  strictly 
necessary  for  the  equilibrium,  since  the  excess  in  the  weight  of  its 
masonry,  from  the  spring  of  the  arch  to  the  key,  and  that  of  the 
upper  part  of  the  tower,  which  also  contributes  to  its  stability,  are 
more  than  sufficient  to  compensate  for  the  weight  of  the  apparatus 
for  illumination,  which  rests  upon  the  summit  of  the  arch.  But  not- 
withstanding this,  as  the  three  openings  in  it  somewhat  diminish  its 
strength,  the  precaution  was  taken,  in  order  to  avoid  the  least  dis- 
placement, to  fasten  all  the  arch  stones  of  the  second  and  third 
courses,  together  with  those  of  the  first,  with  iron  clamps,  one  and 
a  half  inch  thick  by  three  inches  wide,  let  into  the  arch  stones  and 
fastened  to  each  of  them  by  a  bolt,  which  passes  through  two-thirds 
of  their  thickness,  well  secured  with  lead. 


234 

Materials. — The  stone  used  in  the  construction  of  the  tower  was 
taken  from  the  quarries  known  here  by  the  name  of  playa  de  chivos 
immediately  at  the  point  where  the  tower  stands,  and  preferable  to 
the  stone  found  at  any  other  place  in  the  vicinity,  because,  although 
not  of  the  hardest  quality,  they  are  still  sufficiently  so,  and  of  a  more 
equal  and  homogeneous  texture  than  the  others.  Great  care  was 
also  taken  to  use  blocks  of  the  most  durable  kind  in  the  exterior  sur- 
face of  the  wall,  and  for  the  steps  of  the  stairway. 

The  lime  and  sand  employed  were  both  of  excellent  quality;  the 
former  made  of  a  very  hard  and  clean  stone,  and  the  latter  containing 
no  saline  matter.  The  mortar  was  made  with  great  care,  composed 
of  two-fifths  of  lime  and  three-fifths  of  sand,  mixed  with  fresh  water 
and  well  stirred,  so  as  perfectly  to  incorporate  the  ingredients. 

The  doors,  windows,  interior  balustrades,  and  hand  rails  of  the 
staircase  are  of  mahogany. 

After  the  completion  of  the  edifice,  in  order  to  preserve  it  from 
the  effects  of  moisture  and  of  nitrous  salts,  inasmuch  as  the  stone,  as 
already  stated,  is  not  of  the  hardest  kind,  it  was  covered,  both  on 
the  interior  and  exterior  surface,  with  a  very  thin  and  well  laid  coat 
of  painted  stucco. 

The  cost  of  the  structure,  when  completed,  was  very  nearly  that 
calculated  in  the  original  estimate. 


CHAMBER  OF  COMMERCE,  NEW  YORK. 

The  Committee  appointed  to  consider  the  condition  of  the  light-houses  of 
tiie  United  States,  as  developed  in  the  report  of  the  Light-house  Board 
recently  communicated  to  Congress,  ask  leave  to  report : 

That  the  subject  has  attracted  occasional  attention  for  some  years, 
although  your  committee  believe  it  never  received  a  thorough 
investigation  until  the  Light-house  Board  was  appointed  by  the 
Secretary  of  the  Treasury  in  May,  1851,  under  authority  given  by 
Congress.  In  January,  1838,  the  Senate  called  on  the  Treasury 
Department  for  a  copy  of  a  communication  made  by  Messrs.  E.  &  G . 
W.  Blunt,  relative  to  the  light-houses  of  the  United  States,  and  also 
for  a  copy  of  the  report  in  reply  to  that  communication,  made  by 
Mr.  Pleasanton,  the  Fifth  Auditor  of  the  Treasury,  he  being  in 
charge  of  the  whole  light-house  establishment.  In  the  communica- 


235 

tion  of  Messrs.  Blunt,  they  expressed  the  opinion  that  our  establish- 
ment was  badly  managed,  and  was  greatly  inferior  to  the  similar 
establishments  of  France  and  Great  Britain.  In  his  reply,  Mr. 
Pleasanton  undertook  to  show  that  this  opinion  was  not  well  founded, 
and  that  the  charges  accompanying  it  were  frivolous,  unimportant, 
or  groundless.  Messrs.  Blunt  rejoined,  with  a  view  to  prove  that 
their  statements  were  correct.  In  their  first  communication,  Messrs. 
Blunt  took  occasion  to  state  that  the  French  light-houses  were  supe- 
rior to  the  English,  the  former  being  provided  with  lenses  instead  of 
parabolic  reflectors. 

In  May,  1838,  the  Committee  on  Commerce  of  the  Senate  reported 
upon  the  expediency  of  introducing  the  dioptric  apparatus  for  illu- 
minating light-houses  into  the  United  States,  and  upon  the  expedi- 
ency of  improving  the  organization  of  our  light-house  system.  In 
that  report  it  is  stated  that  the  Navy  Board  was  required  at  the  pre- 
vious session  of  Congress  to  examine  the  sites  of  a  large  number  of 
new  light-houses  authorized  at  that  session,  and  inquire  into  the  facts 
concerning  them.  The  act  of  Congress  provided  that  in  cases  where 
objections  were  found  to  exist  the  erection  of  the  buildings  should  be 
suspended.  Under  this  provision  the  Navy  Board  arrested  the  erec- 
tion of  no  less  than  thirty-one  of  the  houses  proposed. 

The  committee  further  stated  that  while  our  light-house  system 
(if  system  it  could  be  called)  had,  probably,  most  of  the  time,  been 
conducted  with  reasonable  care  and  satisfaction  to  the  public  in  most 
respects,  both  the  French  and  English  had,  by  scientific  research 
and  improvement,  perfected  theirs  to  a  considerably  higher  degree. 
The  French  took  the  lead,  under  Fresnel,  who  brought  the  lenticular 
apparatus  into  use.  The  committee  were  satisfied,  with  the  evi- 
dence before  them,  that  this  apparatus  was  the  best  known,  but  to 
test  the  matter  practically,  they  recommended  that  two  sets  of  the 
first  class  and  one  of  the  second  should  be  imported  and  put  up  at 
proper  points  to  try  their  merits  by  actual  experiment. 

Captain  W.  H.  Swift,  of  the  United  States  Topographical  Engi- 
neers, stated,  in  1842,  that  he  had  never  seen  upon  our  coast  a  light 
which  approached,  even  in  a  remote  degree,  the  brilliancy  exhibited 
by  certain  English  lights  Avhich  he  referred  to.  FresnePs  apparatus 
he  considered  superior  to  the  English,  and  both  immeasurably  supe- 
rior to  our  own. 


236 

In  1845,  two  officers  of  the  navy,  viz:  Lieutenants  Jenkins  and 
Bache,  were  sent  to  Europe  by  the  then  Secretary  of  the  Treasury, 
to  obtain  information  concerning  the  light-house  establishments  there. 
In  the  report  of  these  officers,  on  their  return,  they  denounced  our 
lights  as  inferior  to.  all  they- had  seen  abroad;  recommended  strongly 
the  adoption  of  the  French  apparatus,  and  the  appointment  of  a  board 
of  officers  to  devise  some  new  plan  of  light-house  management. 

A  committee  of  the  Franklin  Institute,  of  Philadelphia,  in  May, 
1849,  stated  that  they  were  strongly  impressed  with  the  great  excel- 
lence of  the  Fresnel  system,  a  system  which  had  then  been  estab- 
lished, as  they  said,  in  nearly  three  hundred  places  in  Europe,  where 
it  was  gradually  superseding  the  old  lights,  whilst  in  no  instance  had 
it  been  abandoned  after  it  had  been  once  established. 

The  recent  Light-house  Board  consisted  of  Commodore  Shubrick 
and  Commander  Du  Pont,  of  the  Navy,  General  Totten,  of  the  Engi- 
neers, Colonel  Kearney,  of  the  Topographical  Engineers,  and  Pro- 
fessor Bache,  Superintendent  of  the  Coast  Survey,  as  members,  with 
Lieutenant  Jenkins,  of  the  Navy,  as  Secretary.  Their  report  sets 
forth,  among  other  things,  that  in  1825,  the  French  government 
adopted  definitively  what  is  called  the  French  system  of  illumination, 
and  that  in  1834,  a  new  impulse  was  given  in  England  and  Scotland 
to  light-house  improvement  by  letters  from  Sir  David  Brewster,  and 
by  the  action  of  a  committee  of  the  House  of  Commons.  Although, 
say  the  Board,  the  lens  met  with  much  favor  in  England,  and  has 
been  gradually  getting  into  use,  until  nearly  one-half  the  seacoast 
lights  have  been  changed  since  1837,  still  Scotland  has  introduced  a 
larger  number  in  proportion  to  extent  of  coast.  Following  out  these 
improvements,  another  committee  on  light-houses  was  raised  by  the 
House  of  Commons  in  1845,  and  the  result,  among  other  alleged 
benefits,  has  been  the  introduction  of  a  large  number  of  lens  appa- 
ratus, not  only  into  Great  Britain  but  into  many  of  the  Colonies. 

The  Board,  however,  have  been  unable  to  discover  that  any  steps 
have  been  taken  in  this  country  to  keep  pace  with  the  light-house 
improvements  of  France  and  Great  Britain,  except  the  placing  a 
lens  apparatus  at  the  Highlands  of  Navesink,  an  improved  reflector 
apparatus  in  the  Boston  light-house,  a  lens  of  the  second  class  at 
Sankaty  Head,  Nan  tucket,  and  the  lights  authorized  by  law  to  be 
constructed,  under  the  direction  of  the  Topographical  Bureau,  at 


237 

Brandy  wine  Shoal,  Carysfort  Reef,  and  Sand  Key.  The  law  required 
that  the  lenticular  apparatus  placed  at  Navesink,  and  the  improved 
reflector  apparatus  at  Boston  should  be  tested  by  full  and  satisfactory 
experiment,  as  to  their  merits,  in  comparison  with  the  other  appa- 
ratus in  use.  But  the  Board  have  never  heard  the  result,  nor  that 
any  such  experiment  was  ever  made. 

The  Board,  after  examining  the  subject  committed  to  them  with 
the  patience  and  zeal  its  importance  demanded,  arrived  at  a  great 
number  of  conclusions  set  forth  with  remarkable  particularity  in  their 
report.  They  condemn  most  emphatically  our  whole  system.  They 
distinctly  declare,  that  in  their  judgment  the  light-houses,  light-ves- 
sels, beacons,  and  buoys,  and  their  accessories,  in  the  United  States, 
are  not  as  efficient  as  they  ought  to  be,  and  not  so  much  so  as  those 
of  France  and  Great  Britain.  That  our  light-house  establishment 
does  not  compare  favorably  in  point  of  economy  with  theirs.  That 
the  towers  and  buildings  are  not  constructed,  in  general,  of  the  best 
materials,  nor  with  proper  accommodations.  That  the  lanterns,  as  a 
general  rule,  are  of  improper  dimensions,  constructed  of  ill-adapted 
materials,  without  scientific  skill,  and  are  in  many  instances  not 
suited  to  the  use  designed.  That  there  is  no  systematic  plan  of  con- 
struction, illumination,  and  superintendence.  That  the  illuminating 
apparatus  is  of  a  description  now  nearly  obsolete  where  the  best  of 
that  kind  was  employed  before  the  introduction  of  the  French  lenses. 
That  the  seacoast  reflector  lights  are  in  general  too  low,  and  are 
deficient  in  power  and  range.  That  the  attendance  is  deficient. 
That  the  lights  are  not  properly  classified,  nor  well  distinguished 
from  each  other.  That  there  is  not  in  useful  effect  a  single  first 
class  light  on  the  coast.  That  the  lights  at  Navesink  and  Sankaty 
Head,  Nantucket,  are  the  best.  That  the  Fresnel  lens  is  greatly 
superior  to  any  other  mode  of  light-house  illumination.  That  there 
is  no  proper  system  of  distributing  supplies  to  light-houses,  and  no 
system  in  the  management  of  the  light-house  establishment.  That 
the  light-keepers  in  many  instances  are  not  competent.  That  the 
mode  of  repairs  is  not  efficient  or  reliable.  That  the  floating  lights 
are  comparatively  useless  for  want  of  efficient  lamps  and  reflectors. 
That  the  light-vessels  are  not  well  adapted  to  the  service,  and  are 
not  properly  distinguished  either  by  day  or  by  night.  That  the  buoys 


238 

are  defective  and  the  moorings  insufficient.     And  that  there  is  no 
proper  system  of  beaconage  or  buoyage. 

These  are  but  a  few  of  the  conclusions  of  the  Board.  Yet  these  are 
quite  enough,  if  well  founded,  to  show  that  the  condition  of  the  whole 
light-house  establishment  is  such  as  to  demand  thorough  renovation 
and  reform.  It  is  not  to  be  endured  that  the  lives  of  our  seamen, 
and  of  the  passengers  often  embarked  with  them,  should  ever  be  put 
in  peril  for  Avant  of  the  best  protection  in  approaching  our  ports,  or 
proceeding  along  our  coast,  that  it  is  in  the  power  of  skill,  science  and 
systematic  management  to  give.  Upon  no  consideration  whatever 
ought  the  United  States  to  be  second  to  any  country  under  heaven  in 
affording  all  possible  security  to  the  vast  interests  of  commerce  and 
navigation,  upon  which  so  much  of  national  prosperity  depends. 

For  the  correctness  of  the  positions  taken  by  the  Light-house 
Board,  and  the  sufficiency  of  the  evidence  on  which  they  are  based, 
it  seems  to  your  committee  that  the  high  character,  elevated  stand- 
ing, and  eminent  attainments  of  the  members  of  the  Board  furnish 
an  ample  guarantee.  If  corroborative  testimony  Avere  needed,  more 
than  enough,  in  the  opinion  of  your  committee,  may  be  found  in  the 
various  documents  referred  to  in  this  report.  Still  it  is  due  to  Mr. 
Pleasanton  to  state,  that  in  his  reply  to  the  report  of  the  Light-house 
Board,  he  considers  he  has  shoAvn  that  our  lights  are  satisfactory  to 
the  captains  of  ships  and  pilots  generally;  that  our  light-house  estab- 
lishment is  managed  more  economically  than  that  of  Great  Britain; 
that  our  light-ships  are  superior  to  the  British;  and  that  the  French 
lenses  are  more  expensive,  without  shoAving  a  better  light  "than  the 
reflectors.  It  thus  appears  that  the  parties  stand  in  direct  opposition 
to  each  other.  Both  cannot  be  right.  Your  committee,  after  duly 
considering  the  question,  cannot  avoid  the  conclusion  that  Mr.  Pleas- 
anton is  far  more  likely  to  be  in  error  than  the  Light-house  Board. 

By  way  of  remedy  for  the  evils  they  specify,  the  Board  recom- 
mend among  other  things  the  absolute  adoption  of  the  Fresnel  ap- 
paratus for  all  new  lights  and  all  lights  requiring  renovation,  modi- 
tied  in  special  cases  by  Stevenson's  apparatus.  They  also  recommend 
the  organization  of  a  permanent  Light-house  Board  for  the  construc- 
tion, repair,  management,  and  superintendence  of  the  light-houses, 
light-vessels,  beacons,  and  buoys,  of  the  United  States.  They  pro- 
pose that  this  Board  be  composed  of  the  Secretary  of  the  Treasury, 


239 

as  President,  two  officers  of  the  Navy,  of  high  rank,  one  officer  of 
Engineers,  one  officer  of  Topographical  Engineers,  and  two  civilians 
of  high  scientific  attainments,  as  members,  with  an  officer  of  the 
Navy  and  an  officer  of  Engineers  as  secretaries  ;  the  officers,  civil, 
military,  and  naval,  to  serve  without  additional  salary. 

Your  committee  cannot  doubt  that  the  organization  of  a  Light- 
house Board  of  this  description  would  secure,  beyond  question,  the 
selection  of  proper  sites  for  light-houses  along  our  shores,  with  due 
regard  to  the  wants  of  commerce.  They  are  satisfied  it  would  also 
render  quite  certain  the  proper  construction  of  the  light  towers  and 
buildings,  as  well  as  the  use  of  the  best  illuminating  apparatus. 
They  are  convinced,  too,  it  would  ensure  far  greater  efficiency,  econ- 
omy, and  systematic  management  throughout  the  whole  light-house 
establishment,  than  is  practicable  under  the  superintendence  of  an 
auditor  of  the  Treasury  Department.  A  board  of  skilful,  scientific 
men,  combining  the  variety  of  qualification  required,  is  obviously 
preferable  for  these  purposes,  to  a  disbursing  officer,  not  supposed 
to  be  very  highly  endued  with  engineering,  nautical,  or  optical 
knowledge.  The  fact  stated  by  the  Committee  on  Commerce  of  the 
Senate,  in  1838,  that  the  Navy  Board  stopped  the  erection  of  thirty- 
one  new  light-houses  in  one  year,  for  sufficient  reasons,  indicates 
very  clearly  the  necessity  of  a  proper  light-house  organization  at  all 
times,  even  if  no  stress  be  laid  upon  the  conclusions  of  the  recent 
able  Light-house  Board.  This  necessity  is  certainly  not  lessened  by 
the  further  facts  that  the  present  superintendent  has  omitted  to  test 
the  merits  of  the  Fresnel  apparatus,  as  virtually  directed  by  the  act 
of  Congress  of  1838,  and  that  he  still  strenuously  opposes  the  more 
frequent  selection  of  that  apparatus  for  the  use  of  our  light-houses, 
in  the  face  of  a  wreight  of  testimony  in  its  favor,  which  to  your 
committee  appears  irresistible.  This  course  plainly  discovers  a 
steadfast  determination  on  his  part  against  reform  and  improvement, 
far  removed,  as  your  committee  think,  from  the  true  spirit  which 
should  actuate  the  head  of  so  important  an  establishment.  In  any 
view  your  committee  are  able  to  take  of  the  subject,  the  proposed 
change  seems  highly  expedient.  They  therefore  recommend  the 
adoption  of  the  accompanying  resolution. 

All  which  is  respectfully  submitted. 

GEO.   CURTIS, 

LEOPOLD  BIERWIRTH,    [  Committee. 

JAMES  W.  PHILLIPS, 


240 

Resolved,  That  the  Chamber  of  Commerce  of  the  City  of  New 
York  cordially  approves  of  the  recommendation  of  the  Light-house 
Board,  contained  in  their  report  of  30th  of  January  last,  that  a  per- 
manent board  be  organized,  to  be  charged  by  law  with  the  entire 
management  of  the  light-house  establishment  of  the  United  States  ; 
and  that  the  Chamber  sincerely  hopes  that  Congress  will  carry  that 
recommendation  into  effect. 

At  a  meeting  of  the  Chamber  of  Commerce  at  New  York,  held 
on  the  4th  May,  1852,  the  preceding  report  and  resolution  were 
approved,  and  ordered  to  be  printed  and  sent  to  the  Senate  and 
House  of  Representatives  as  the  sense  of  the  Chamber. 

MOSES  H.  GRINNELL,  President. 

M.  MAURY,  Secretary. 


ROYAL  INSTITUTION  OF  GREAT  BRITAIN. 
WEEKLY  EVENING  MEETING. — FRIDAY  MARCH  9,   1860. 

The  Lord  Wensleydale,    Vice  President,   in  the    Chair. — Professor 
Faraday,  D.  C.  L.  F.  R.  S. 

On  Light-house  Illumination — The  Electric  Light. 

The  use  of  light  to  guide  the  mariner  as  he  approaches  land,  or 
passes  through  intricate  channels,  has,  with  the  advance  of  society, 
and  its  ever  increasing  interests,  caused  such  a  necessity  for  means 
more  and  more  perfect,  as  to  tax  to  the  utmost  the  powers  both  of 
the  philosopher  and  the  practical  man,  in  the  development  of  the  prin- 
ciples concerned,  and  their  efficient  application.  Formerly  the  means 
were  simple  enough;  and  if  the  light  of  a  lanthorn  or  torch  was  not 
sufficient  to  point  out  a  position,  a  fire  had  to  be  made  in  their  place. 
As  the  system  became  developed,  it  soon  appeared  that  power  could 
be  obtained,  not  merely  by  increasing  the  light  but  by  directing  the 
issuing  rays:  and  this  was  in  many  cases  a  more  powerful  and  useful 
means  than  enlarging  the  combustion — leading  to  the  diminution  of 
the  volume  of  the  former  with,  at  the  same  time,  an  increase  in  its 
intensity.  Direction  was  obtained,  either  by  the  use  of  lenses  de- 
pendent altogether  upon  refraction,  or  of  reflectors  dependent  upon 
metallic  reflexion;  and  some  ancient  specimens  of  both  were  shown. 


In  modern  times  the  principle  of  total  reflexion  has  also  been  em- 
ployed, which  involves  the  use  of  glass,  and  depends  both  upon  re- 
fraction and  reflexion.  In  all  these  appliances  much  light  is  lost:  if 
metal  be  used  for  reflexion,  a  certain  proportion  is  absorbed  by  the 
face  of  the  metal;  if  glass  be  used  for  refraction,  light  is  lost  at  all 
the  surfaces  where  the  ray  passes  between  the  air  and  the  glass;  and 
also  in  some  degree  by  absorption  in  the  body  of  the  glass  itself. 
There  is,  of  course,  no  power  of  actually  increasing  the  whole  amount 
of  light,  by  any  optical  arrangement  associated  with  it. 

The  light  which  issues  forth  into  space  must  have  a  certain  amount 
of  divergence.  The  divergence  in  the  vertical  direction  must  be 
enough  to  cover  the  sea  from  the  horizon,  to  within  a  certain  mod- 
erate distance  from  the  shore,  so  that  all  ships  within  that  distance 
may  have  a  view  of  their  luminous  guide.  If  it  have  less,  it  may  es- 
cape observation  where  it  ought  to  be  seen;  if  it  have  more,  light  is 
thrown  away  which  ought  to  be  directed  within  the  useful  degree  of 
divergence;  or  if  the  horizontal  divergence  be  considered,  it  may  be 
necessary  so  to  construct  the  optical  apparatus,  that  the  light  within 
an  angle  of  60°  or  45°  shall  be  compressed  into  a  beam  diverging  only 
15°,  that  it  may  give  in  the  distance  a  bright  flash  having  a  certain 
duration  instead  of  a  continuous  light — or  into  one  diverging  only  5° 
or  6°,  which,  though  of  far  shorter  duration,  has  greatly  increased 
intensity  and  penetrating  power  in  hazy  weather.  The  amount  of 
divergence  depends  in  a  large  degree  upon  the  bulk  of  the  source  of 
light,  and  cannot  be  made  less  than  a  certain  amount,  with  the  flame 
of  a  given  size.  If  the  flame  of  an  Argand  lamp  f  th  of  an  inch  wide, 
and  1|  inch  high,  be  placed  in  the  focus  of  an  ordinary  Trinity  House 
parabolic  reflector,  it  will  supply  a  beam  having  about  15°  diverg- 
ence; if  we  wish  to  increase  the  effect  of  brightness,  we  cannot  prop- 
erly do  it  by  enlarging  the  lamp  flame;  for  though  lamps  are  made 
for  the  dioptric  arrangement  of  Fresnel,  which  have  as  many  as  four 
wicks,  flames  3£  inches  wide,  and  burn  like  intense  furnaces,  yet  if 
one  be  put  into  the  lamp  place  of  the  reflector  referred  to,  its  eifect 
would  chiefly  be  to  give  a  beam  of  wider  divergence;  and  if  to  cor- 
rect this,  the  reflector  were  made  with  a  greater  focal  distance,  then 
it  must  be  altogether  of  a  much  larger  size.  The  same  general  result 
occurs  with  the  dioptric  apparatus;  and  here,  where  the  four- wicked 
lamps  are  used,  they  are  placed  at  times  nearly  40  inches  distant  from 
18 


242 

the  lens,  occasioning  the  necessity  of  a  very  large,  though  very  fine, 
glass  apparatus. 

On  the  other  hand,  if  the  light  could  be  compressed,  the  necessity 
for  such  large  apparatus  would  cease,  and  it  might  be  reduced  from 
the  size  of  a  room  to  the  size  of  a  hat;  and  here  it  is  that  we  seek  ir* 
the  electric  spark,  and  such  like  concentrated  sources  of  light,  for  aid 
in  illumination.  It  is  very  true,  that  by  adding  lamp  to  lamp,  each 
with  its  reflector,  upon  one  face  or  direction,  power  can  be  gained ; 
and  in  some  of  the  revolving  lights,  ten  lamps  and  reflectors  unite  to- 
give  the  required  flash.  But  then  not  more  than  three  of  these  faces 
can  be  placed  in  the  whole  circle;  and  if  a  fixed  light  be  required  in 
all  directions  round  the  light-house  nothing  better  has  been  yet  es- 
tablished than  the  four-wicked  Fresnel  lamp  in  the  centre  of  its  diop- 
tric and  catadioptric  apparatus.  Now  the  electric  light  can  be  raised 
up  easily  to  an  equality  with  the  oil  lamp,  and  if  then  substituted  for 
the  latter,  will  give  all  the  effect  of  the  latter;  or  by  expenditure  of 
money  it  can  be  raised  to  a  five  or  tenfold  power,  or  more,  and  will 
then  give  five  or  tenfold  effect.  This  can  be  done,  not  merely  with- 
out increase  of  the  volume  of  the  light,  but  whilst  the  light  shall 
have  a  volume  scarcely  the  2000th  part  of  that  of  the  oil  flame. 
Hence,  the  extraordinary  assistance  we  may  expect  to  obtain  of  di- 
minishing the  size  of  the  optical  apparatus  and  perfecting  that  part 
of  the  apparatus. 

Many  compressed  intense  lights  have  been  submitted  to  the  Trinity 
House ;  and  that  corporation  has  shown  its  great  desire  to  advance 
all  such  objects  and  improve  the  lighting  of  the  coast,  by  spending, 
upon  various  occasions,  much  money  and  much  time  for  this  end.  It 
is  manifest  that  the  use  of  a  light-house  must  be  never  failing,  its 
service  ever  sure ;  and  that  the  latter  cannot  be  interfered  with  by 
the  introduction  of  any  plan,  or  proposition,  or  apparatus,  wrhich  has 
not  been  developed  to  the  fullest  possible  extent,  as  to  the  amount  of 
light  produced — the  expense  of  such  light,  the  wear  and  tear  of  the 
apparatus  employed,  the  steadiness  of  the  light  for  16  hours,  its  lia- 
bility to  extinction,  the  amount  of  necessary  night  care,  the  number 
of  attendants,  the  nature  of  probable  accidents,  its  fitness  for  secluded 
places,  and  other  contingent  circumstances,  which  can  as  well  be  as- 
certained out  of  a  light-house  as  in  it.  The  electric  spark  which  has 
been  placed  in  the  South  Foreland  High  Light,  by  Professor  Holmes, 


243 


to  do  duty  for  the  six  winter  months,  had  to  go  through  all  this  pre- 
paratory education  before  it  could  be  allowed  this  practical  trial.  It 
is  not  obtained  from  frictional  electricity,  or  from  voltaic  electricity, 
but  from  magnetic  action.  The  first  spark  (and  even  magnetic  elec- 
tricity as  a  whole)  was  obtained  28  years  ago.  (Faraday,  Philosoph- 
ical Transactions,  1832,  p.  32.)  If  an  iron  core  be  surrounded  by  wire, 
and  then  moved  in  the  right  direction  near  the  poles  of  a  magnet,  a 
current  of  electricity  passes,  or  tends  to  pass,  through  it.  Many 
powerful  magnets  are  therefore  arranged  on  a  wheel,  that  ^hey  may 
be  associated  very  near  to  another  wheel,  on  which  are  fixed  many 
helices  with  their  cores,  like  that  described.  Again,  a  third  wheel 
consists  of  magnets  arranged  like  the  first;  next  to  this  is  another 
wheel  of  the  helices,  and  next  to  this  again  a  fifth  wheel,  carrying 
magnets.  All  the  magnet  .wheels  are  fixed  to  one  axle,  and  all  the 
helix  wheels  are  held  immovable  in  their  place.  The  wires  of  the 
helices  are  conjoined  and  connected  with  a  commutator,  which,  as 
the  magnet-wheels  are  moved  round,  gathers  the  various  electric  cur- 
rents produced  in  the  helices,  and  sends  them  up  through  two  insu- 
lated wires  in  one  common  stream  of  electricity  into  the  light-house 
lanthorn.  So  it  will  be  seen  that  nothing  more  is  required  to  pro- 
duce electricity  than  to  revolve  the  magnet-wheels.  There  are  two 
magneto-electric  machines  at  the  South  Foreland,  each  being  put  in 
motion  by  a  two-horse  power  steam-engine ;  and,  excepting  wear  and 
tear,  the  whole  consumption  of  material  to  produce  the  light  is  the 
coke  and  water  required  to  raise  steam  for  the  engines,  and  carbon 
points  for  the  lamp  in  the  lanthorn. 

The  lamp  is  a  delicate  arrangement  of  machinery,  holding  the  two 
carbons  between  which  the  electric  light  exists,  and  regulating  their 
adjustment;  so  that  whilst  they  gradually  consume  away,  the  place  of 
the  light  shall  not  be  altered.  The  electric  wires  end  in  the  two  bars 
of  a  small  railway,  and  upon  these  the  lamp  stands.  When  the  car- 
bons of  a  lamp  are  nearly  gone,  that  lamp  is  lifted  off  and  another 
instantly  pushed  into  its  place.  The  machines  and  lamp  have  done 
their  duty  during  the  past  six  mouths  in  a  real  and  practical  manner. 
The  light  has  never  gone  out,  through  any  deficiency  or  cause  in  the 
engine  and  machine  house;  and  when  it  has  become  extinguished  in 
the  lanthorn,  a  single  touch  of  the  keeper's  hand  has  set  it  shining  as 
bright  as  ever.  The  light  shown  up  and  down  the  channel,  and  across 


244 

into  France,  with  a  power  far  surpassing  that  of  any  other  fixed  light 
within  sight,  or  anywhere  existent.  The  experiment  has  been  a  good 
one.  There  is  still  the  matter  of  expense  and  some  other  circumstances 
to  be  considered;  but  it  is  the  hope  and  desire  of  the  Trinity  House, 
and  all  interested  in  the  subject,  that  it  should  ultimately  justify  its 
full  adoption. 

[M.  P.] 


THE    LIGHT   DUES    LEVIED    ON    THE    SHIPPING    OF    THE 
UNITED   STATES   IN    GREAT   BRITAIN. 

CORRESPONDENCE    RESPECTING    THE    LIGHT    DUES    LEVIED     ON    AMERICAN 
SHIPPING   IN   THE   UNITED    KINGDOM. 

No.    1. 

Mr.  Lawrence  to  Viscount  Palmerston. — (Received  January  2,  1851.) 

UNITED  STATES  LEGATION, 
138  PICCADILLY,  December  31,  1850. 

The  undersigned,  Envoy  Extraordinary  and  Minister  Plenipoten- 
tiary of  the  United  States  of  America,  has  the  honor,  under  instruc- 
tions from  his  government,  to  invite  the  attention  of  Viscount 
Palmerston,  her  Majesty's  Principal  Secretary  of  State  for  Foreign 
Affairs,  to  the  subject  of  the  light  dues  exacted  of  the  mercantile 
marine  of  the  United  States  entering  the  ports  of  the  United  King- 
dom. 

It  is  nearly  two  years  since  her  Majesty's  government  determined 
to  respond  to  the  invitation  of  the  United  States,  made  to  the  world 
many  years  ago,  and  recommend  Parliament  to  repeal  the  prohibitory 
navigation  laws  of  the  kingdom  ;  and  the  commerce  of  the  two 
nations  has  been  conducted  for  now  just  one  year  on  the  reciprocal 
basis  established  in  accordance  with  such  recommendation.  The 
United  States  ask  Great  Britain  to  carry  out  this  principle;  to  estab- 
lish reciprocity  in  fact  as  well  as  in  name,  to  do  justice  to  the  com- 
merce of  the  United  States. 

The  light-houses,  floating-lights,  buoys,  and  beacons  on  the  whole 
sea  and  lake-coast,  and  rivers  of  the  United  States,  were  con- 
structed and  are  maintained  by  the  federal  government,  an  annual 
appropriation  being  made  by  Congress  for  these  objects.  No  light 


245 

dues  of  any  kind  are  levied,  either  on  vessels  of  the  United  States 
or  on  ships  of  foreign  nations.  In  the  year  1792  there  were  but  10 
lights  in  the  Union.  In  the  year  1848  there  were  270  light-houses, 
30  floating  lights,  and  1,000  buoys,  besides  numerous  fixed  beacons. 
There  are  probably  at  this  time,  including  those  under  construction 
on  the  Pacific  coast,  more  than  300  light-houses,  with  a  propor- 
tionate number  of  floating  lights,  buoys,  &c.,  all  of  which  are  given 
to  the  use  of  the  world  by  the  United  States  without  tax  or  charge. 

The  commerce  of  the  United  States  is  not  met  with  a  correspond- 
ing liberality  in  the  ports  of  the  United  Kingdom.  The  reciprocity 
intended  to  be  established  by  the  navigation  law  of  last  year,  and  so 
much  to  be  wished  for  between  the  two  greatest  commercial  nations 
of  the  globe,  will  not  be  realized  if  American  tonnage  continues  sub- 
jected to  onerous  light  dues  in  Great  Britain,  while  British  vessels 
enjoy  without  pay  the  lights,  <fec.,  upon  the  coast  of  the  United  States. 

The  undersigned  is  not  unaware  that  the  system  of  light  dues  in 
this  country  is  somewhat  complicated,  but  he  believes  that  as  reforms 
have  been  made  in  many  other  laws  and  customs  adopted  in  former 
ages  under  a  different  state  of  society,  so  changes  can  be  made  in 
these,  adapting  them  more  to  the  present  condition  of  the  world  and 
to  the  liberal  policy  of  other  nations. 

In  illustration  of  the  onerous  and  unequal  operation  of  the  present 
system  of  lights  in  Great  Britain  upon  American  commerce,  the  un- 
dersigned has  the  honor  to  ask  Viscount  Palmerston's  attention  to  a 
few  examples: 

The  American  mail-steamers  entering  at  Liverpool  pay  for  light 
dues  the  sum  of  62Z.  for  each  voyage.  If  the  British  steamers  were 
subjected  to  the  same  charge  in  American  ports,  it  would  amount 
annually  to  the  great  sum  of  3,224Z.  Two  steamers,  the  "Washing- 
ton" and  "Hermann,"  returning  from  New  York  to  Bremen,  and 
touching  on  the  way  at  Southampton,  paid  last  year  light  dues  to  the 
amount  of  800Z.,  including  the  charge  for  the  Heligoland  light,  which 
the  undersigned  is  informed  they  have  never  seen.  The  steamer 
"Franklin,"  running  between  New  York  and  Havre,  and  touching 
at  Cowes,  but  without  anchoring,  merely  to  land  its  mails,  has  been 
subjected  to  light  dues,  which  have  been  paid  by  order  of  the  Trinity 
House,  but  under  protest  of  the  consignees.  One  commercial  house 
in  New  York,  running  sixteen  ships  between  that  port,  Liverpool, 
and  London,  paid  last  year  for  such  dues,  2,498L  3s.  6d.  Another 
American  shipping  house  paid  for  lights  in  1849  the  sum  of  2,252?. 


246 

The  undersigned  will  not  multiply  individual  examples  of  the 
amount  of  this  tax.  The  number  of  American  ships  that  entered  the 
ports  of  the  United  Kingdom  for  the  nine  months  ending  October  1, 
1850,  was  six  hundred  and  two  (602,)  with  a  tonnage  of  four  hundred 
and  seventy-three  thousand  nine  hundred  (473,900.)  If  one-third  be 
added  for  the  last  quarter  of  the  year,  the  total  will  be  seven  hundred 
and  fifty-two  (752)  ships,  and  about  six  hundred  thousand  tons,  being 
an  average  of  nearly  eight  hundred  (800)  tons  to  each  ship.  Assum- 
ing this  calculation  to  be  substantially  correct,  it  appears  from  the 
Trade  List,  that  three  thousand  nine  hundred  and  nine  (3,909)  Amer- 
ican vessels  have  entered  the  ports  of  the  United  Kingdom  in  the 
last  four  years,  with  a  tonnage  of  two  millions  four  hundred  and 
twenty-two  thousand  four  hundred  and  ninety-two  (2,422,492.) 
During  the  last  ten  years,  the  number  of  American  vessels  en- 
tered in  the  United  Kingdom  has  been  seventy-eight  hundred  and 
seventy-two  (7,872,)  with  an  aggregate  of  four  million  six  hundred 
and  eighty-one  thousand  nine  hundred  and  twenty-five  (4,681,925) 
tons. 

The  light  dues  are  not  the  same  in  all  the  ports  of  the  United 
Kingdom.  The  rate  at  Liverpool  is  ten  pence  halfpenny  (lO^c?.)  or 
eleven  pence  (lie?.,)  whereas  the  charge  in  London  is  thirteen  pence 
(13d)  per  ton.  If  the  average  is  taken  at  one  shilling  (Is.)  per  ton, 
a  ship  of  eight  hundred  (800)  tons  would  pay  forty  pounds  (40Z.,)  and 
seven  hundred  and  fifty-two  (752)  ships,  with  six  hundred  thousand 
(600,000)  tons  register,  would  pay  about  thirty  thousand  pounds 
(30,0002.,)  or  one  hundred  and  forty-six  thousand  dollars  ($146,000) 
annually,  and  it  is  not  probable  that  the  amount  of  tonnage  will 
decrease  in  coming  years.  Thirty-nine  hundred  and  nine  (3,909) 
American  ships  must  have  paid  with  a  tonnage  of  two  millions 
four  hundred  and  twenty-two  thousand  four  hundred  and  ninety- 
two  (2,422,492,)  the  sum  of  one  hundred  and  twenty-one  thousand 
pounds  (121,0002.,)  or  nearly  six  hundred  thousand  dollars  ($600,000.) 
And  within  ten  years  last  past,  the  shipping  of  the  United  States  has 
contributed,  upon  seven  thousand  eight  hundred  and  seventy-two 
(7,872)  vessels,  the  aggregate  tonnage  of  which  was  four  million  six 
hundred  and  eighty-one  thousand  nine  hundred  and  twenty-five 
(4,681,925,)  the  immense  sum  of  two  hundred  and  thirty-four  thou- 
sand pounds  (234,000?.,)  or  over  one  million  one  hundred  thousand 
dollars  ($1,100,000,)  for  the  support  of  the  light-house  system  of  the 
United  Kingdom. 


247 

Daring  the  last  year  there  appears  to  have  been  levied  upon  the 
shipping  of  the  world  for  the  light  dues  in  the  United  Kingdom, 
between  four  and  five  hundred  thousand  pounds.  Of  this,  one-four- 
teenth part  was  paid  by  citizens  of  the  United  States;  while  British 
subjects,  with  a  fleet  doubtless  equally  large  in  the  ports  of  the  Uni- 
ted States,  have  not  been  taxed  at  all  for  the  maintenance  of  lights. 
The  government  of  the  United  States,  in  view  of  its  liberality,  is 
justified  in  asking  her  Majesty's  government  to  do  away  with  this 
great  inequality,  and  remove  this  restriction  on  commerce. 

The  undersigned  believes  that  no  other  nation  levies  so  heavy  a 
tax  upon  ships  in  the  form  of  light  dues  as  this.  There  are  in  the 
United  States  many  more  light-houses,  <fcc.,  than  in  the  United 
Kingdom;  yet  the  annual  appropriation  for  the  construction  of  new, 
the  repair  of  old,  light-houses,  and  the  maintenance  of  both,  does 
not  equal  one-fifth  of  the  animal  amount  raised  for  this  purpose  in 
the  United  Kingdom  by  the  tax  on  the  shipping  coming  into  its 
ports. 

In  conclusion,  the  undersigned,  on  behalf  of  his  government, 
expresses  the  wish  that  her  Majesty's  government  may  take  this 
grave  subject  into  consideration;  that  it  may  speedily  set  free  Amer- 
ican shipping  from  so  unequal  and  so  onerous  a  restriction  ;  that  it 
may  complete  its  great  measures  for  commercial  freedom;  and  may 
thus  increase  still  more  the  intercommunication  which  is  already 
producing  so  happy  results. 

The  undersigned,  &c.  (Signed) 

ABBOTT  LAWRENCE. 


No.  2. 
Viscount  Palmerston  to  Mr.  Lawrence. 

FOREIGN  OFFICE,  February  6,  1851. 

The  undersigned,  &c.,  has  the  honor  to  inform  Mr.  Lawrence, 
&c.,  that  her  Majesty's  government  has  had  under  its  consideration 
the  note  which  Mr.  Lawrence  addressed  to  the  undersigned  on  the 
31st  of  December,  complaining  that  heavy  light  dues  are  levied 
on  American  shipping  in  the  ports  of  the  United  Kingdom,  whilst 
no  dues  of  the  same  kind  are  charged  upon  British  ships  frequent- 
ing the  ports  of  the  United  States  ;  and  Mr.  Lawrence  says  that  he 


248 

is  instructed  by  his  government  to  request  that  measures  may  be- 
taken in  order  that  American  vessels  may  enjoy  in  British  ports,  in 
regard  to  exemption  both  from  light  dues  and  from  other  similar 
charges,  the  same  advantages  which  British  vessels  enjoy  in  the 
ports  of  the  United  States. 

In  reply,  the  undersigned  has  the  honor  to  state,  that  the  differ- 
ence between  the  treatment  of  British  vessels  in  American  ports, 
and  that  of  American  vessels  in  British  ports  in  regard  to  light 
dues,  is  a  consequence  of  the  difference  which  exists  between  the  sys- 
tem on  which  coast  lights  are  maintained  in  the  United  States  and  the 
system  on  which  such  lights  are  maintained  in  the  United  Kingdom. 
In  the  United  States  the  coast  lights  are  erected  and  maintained 
by  the  federal  government,  and  the  expenses  connected  with  those 
lights  form  part  of  the  general  expenditure  of  that  government. 
The  federal  government,  therefore,  has  a  right  to  determine 
whether  it  shall  reimburse  itself  for  this  outlay  by  levying  light 
dues  upon  shipping,  or  whether,  on  the  whole,  it  may  not  be  more 
for  the  advantage  of  the  United  States,  and  more  conducive  to  the 
commercial  prosperity  of  the  nation,  that  this  charge  should  be 
borne  by  the  public  revenue,  and  that  the  commerce  of  the  Union 
should  be  freed  from  any  burthen  in  the  shape  of  light  dues  upon 
vessels  frequenting  the  ports  of  the  Union.  The  government  of 
the  United  States  having  power  to  decide  this  question,  has  deter- 
mined, wisely,  as  her  Majesty's  government  think,  as  well  as  liber- 
ally, to  free  the  commerce  of  the  Union  from  any  burthen  on  this 
account,  and  to  defray  out  of  the  national  revenue  the  actual  cost  of 
erecting  and  maintaining  the  coast  lights. 

If  the  coast  lights  of  the  United  Kingdom  had  been  established 
upon  the  same  principle,  and  if  they  had  been  erected  and  were 
maintained  at  the  public  expense,  and  if  they  were  managed  and 
administered  by  a  department  of  the  State,  it  is  possible  that  her 
Majesty's  government  might  think  that  it  would  be  best  for  the 
general  interests  of  the  nation,  that  the  system  of  the  United  States 
in  regard  to  these  matters  should  be  adopted  in  this  country,  and 
that  the  commerce  of  the  United  Kingdom  should  be  relieved  from 
the  burthen  of  light  dues. 

But  the  British  government  has  not  the  power  to  deal  with  this 
matter  as  it  pleases.  The  various  lights  which  are  established  round 
the  coasts  of  the  United  Kingdom  have  been  erected  and  are  main- 
tained by  various  corporate  bodies  ;  and  those  corporate  bodies  are 
entitled,  by  patents  and  by  acts  of  Parliament,  to  levy  certain  dues 


249 

upon  shipping,  in  order  to  raise  the  necessary  income  for  paying  in- 
terest on  the  capital  laid  out  in  the  construction  of  the  lights,  and 
for  providing  the  means  requisite  for  defraying  the  expense  of  main- 
taining those  lights. 

Her  Majesty's  government  have  no  right  or  power  to  order  these 
corporate  bodies  to  abstain  from  levying  these  dues  ;  and  these  dues 
could  not  be  made  to  cease  unless  Parliament  was  to  vote  such  sums 
as  would  be  necessary  to  buy  up  for  the  public  the  interest  which 
the  private  parties  concerned  have  in  these  lights  ;  nor  unless  Par- 
liament were  at  the  same  time  to  authorize  the  government  to 
abolish  light  dues  for  the  future,  and  were  to  charge  upon  the 
public  revenue  the  expense  of  maintaining  the  lights. 

The  expediency  of  adopting  such  a  course  has,  indeed,  from  time 
to  time,  been  suggested,  but  the  question  has  not  hitherto  been  con- 
sidered with  a  view  to  any  practical  decision. 

Her  Majesty's  government,  however,  cannot  admit  that  the  differ 
ence  which  exists  between  the  system  which  prevails  in  the  United 
States  and  that  which  subsists  in  Great  Britain,  in  regard  to  coast 
lights,  has  the  effect  of  infringing  upon  that  principle  of  commercial 
reciprocity  between  Great  Britain  and  the  United  States  which 
forms  the  basis  of  the  treaty  of  1815.  It  is  no  part  of  the  engage- 
ments of  that  treaty,  that  the  internal  system  and  local  arrange- 
ments of  the  two  countries  upon  commercial  matters  shall  be  the 
same.  But  the  principle  distinctly  laid  down  in  the  second  para- 
graph of  the  1st  article  of  the  treaty  of  1815,  is,  that  the  vessels 
of  each  country  shall,  in  the  ports  of  the  other,  be  treated  in  regard 
to  duties  and  charges,  in  the  same  manner  and  on  the  same  footing 
as  national  vessels  ;  and  this  stipulation  is  strictly  observed  in  re- 
gard to  the  light  dues  which  are  levied  upon  American  vessels  in 
British  ports,  for  no  other  or  higher  light  dues  are  levied  in  those 
ports  upon  American  vessels  than  are  levied  in  those  ports  upon  ves- 
sels belonging  to  the  United  Kingdom. 

But  if  the  British  light  dues  cannot  be  deemed  to  be  any  in- 
fringement of  the  principle  of  reciprocity  which  forms  the  basis  of 
the  treaty  of  1815,  neither  can  they  be  considered  as  in  any  de- 
gree conflicting  with  the  liberal  principle  upon  which  the  present 
navigation  law  of  Great  Britain  is  founded.  For  that  navigation 
law  relates  to  the  admission  of  foreign  ships  into  British  ports  with 
certain  goods  on  board,  and  coming  from  certain  voyages,  which 
goods  and  voyages  would  before  the  passing  of  that  law,  have  in- 
volved an  exclusion  from  a  British  port ;  but  that  law  has  no  refer- 


250 

ence  to  light  dues  or  harbor  dues,  nor  does  it  make  any  mention  of 
such  matters,  and  it  cannot,  therefore,  be  appealed  to  as  requiring 
for  its  complete  execution,  that  any  change  should  be  made  in  such 
matters. 

Her  Majesty's  government  are  quite  ready  to  discuss  with  the 
government  of  the  United  States  any  question  which  may  arise  in 
regard  to  any  supposed  incompleteness  in  the  mutual  application  of 
that  principle  of  reciprocity  in  matters  of  navigation  which  is  con- 
tained in  the  act  12  and  13  Viet.,  cap.  29  ;  but  willing  and  desi- 
rous as  they  are  to  carry  out  the  provisions  of  that  act  to  the  fullest 
extent  with  respect  to  all  countries  which  are  disposed,  as  the  United 
States  have  declared  themselves  to  be,  to  pursue  a  similar  course, 
yet  her  Majesty's  government  cannot  admit  the  force  of  arguments 
founded  upon  a  constructive  application  of  that  law  to  matters 
which  are  wholly  beyond  the  range  of  its  enactments. 

The  undersigned,  &c.  (Signed)  PALMERSTON. 


No.   3. 
Mr.  Lawrence  to  Viscount  Palmerston. 

UNITED  STATES  LEGATION, 
138  PICCADILLY,  February  12,  1851. 

The  undersigned,  Envoy  Extraordinary  and  Minister  Plenipoten- 
tiary of  the  United  States  of  America,  has  the  honor  to  acknowledge 
the  receipt  of  the  note  of  Viscount  Palmerston,  Her  Britannic  Ma- 
jesty's Principal  Secretary  of  State  for  Foreign  Affairs,  of  the  6th 
instant,  in  reply  to  the  former  note  of  the  undersigned  to  Lord 
Palmerston,  on  the  subject  of  the  imposition  of  light  dues  on  the 
tonnage  of  the  United  States  within  the  ports  of  the  United  King- 
dom, and  will  not  ff.il  to  transmit  a  copy  to  his  government  by  the 
earliest  opportunity. 

The  undersigned  avails  himself  of  this  occasion  to  correct  an 
error  into  which  Her  Majesty's  government  seem  to  have  fallen  with 
reference  to  the  request  made  by  the  undersigned,  on  behalf  of  the 
government  of  the  United  States,  on  this  subject. 

The  government  of  the  United  States  is  not  unaware  of  the  dif- 
ference between  the  system  on  which  coast  lights  are  maintained  in 
the  United  States  and  the  system  on  which  such  lights  are  main- 
tained in  the  United  Kingdom,  On  the  contrary,  the  undersigned 


251 

alluded  to  that  difference  in  the  former  communication  he  had  the 
honor  to  make  to  Viscount  Palmerston  with  reference  to  them. 
That  fact  does  not,  however,  diminish  the  pressure  of  this  tax  upon 
the  shipping  of  the  United  States.  And  while  the  undersigned  dis- 
claims all  intention  of  discussing  the  particular  mode  by  which  the 
lights  of  the  United  Kingdom  are  maintained,  he  still  cherishes  the 
hope  that  there  is  nothing  in  that  system  to  prevent  the  changes  for 
which  his  government  have  asked. 

The  federal  government  does  not  rest  this  request  on  the  pro- 
visions of  the  convention  of  1815.  Lord  Palmerston  justly  says, 
that  "  it  is  no  part  of  the  engagements  of  that  treaty,  that  the  in- 
ternal system  and  local  arrangements  of  the  two  countries  upon 
commercial  matters  shall  be  the  same." 

Neither  does  it  seek  to  view  the  present  navigation  law  of  the 
United  Kingdom  as  liberating  the  commerce  of  the  United  States 
from  this  tax.  Were  that  the  case,  there  would  have  been  no  occa- 
sion to  instruct  the  undersigned  to  make  the  communication  of  the 
31st  of  December  last. 

The  federal  government  rests  this  request  solely  on  the  fact  that 
the  commerce  of  Great  Britain  enjoys  without  charge  the  lights, 
beacons,  and  buoys  maintained  by  the  United  States  on  a  coast 
several  thousand  miles  in  extent;  while  the  commerce  of  the  United 
States  is  heavily  taxed  for  the  support  of  similar  lights,  beacons,  and 
buoys  in  the  United  Kingdom.  In  view  of  this  fact,  it  asks  Her 
Majesty's  government  to  meet  the  liberality  of  the  United  States 
with  a  reciprocal  liberality.  And  as  an  additional  reason  for  granting 
the  request,  it  points  to  the  present  commercial  policy  of  the  two 
nations,  founded  professedly  on  the  principle  of  reciprocity;  and  it 
invites  Her  Majesty's  government  to  extend  the  principle  still  fur- 
ther, and  treat  the  commerce  of  the  United  States  as  liberally  as  the 
United  States  treat  the  commerce  of  the  United  Kingdom. 

The  undersigned  trusts  that  no  question  will  arise  in  regard  to  any 
supposed  incompleteness  in  the  mutual  application  of  that  principle 
of  reciprocity  in  matters  of  navigation  contained  in  the  act  12  and 
13  Viet.,  cap.  29,  to  render  necessary  the  discussion  for  which 
Viscount  Palmerston  expresses  the  readiness  of  Her  Majesty's  gov- 
ernment. 

The  undersigned  has  great  pleasure  in  learning  that  the  expedi- 
ency of  adopting  such  a  course  as  that  of  the  United  States  has  been 
from  time  to  time  suggested,  and  renews  the  expression  of  the  hope 


252 

that  Her  Majesty's  government  may  devise  some  way  to  remove  or  to 
lighten  this  burden,  which  now  falls  so  heavily  on  the  commerce  of 
the  United  States. 
The  undersigned,  <fec., 

ABBOTT  LAWRENCE. 


No.    4. 
Viscount  Palmerston  to  Mr.  Lawrence. 

FOREIGN  OFFICE,   February  14,   1851. 

The  undersigned,  &c.,  has  the  honor  to  inform  Mr.  Lawrence,  &c.. 
that  he  has  received  and  has  referred  to  the  proper  department  of 
Her  Majesty's  government,  the  note  which  Mr.  Lawrence  addressed 
to  the  undersigned  on  the  12th  instant,  relative  to  the  light  dues 
which  are  levied  on  American  shipping  in  the  ports  of  the  United 
Kingdom. 

The  undersigned,  &c., 

PALMERSTON. 


REPORT    OF    THE    LIGHT-HOUSE    BOARD 

TO  THE  SECRETARY  OF  THE  TREASURY, 

In  answer  to  a  resolution  of  the  Senate  of  February  1,  1858,  calling  upon 
the  Department  for  information  in  regard  to  the  expense  of  erecting 
liglit-liouses,  &c. 

TREASURY  DEPARTMENT, 
Office  Light-house  Board,  March  13,  1858. 

SIR  :  I  have  the  honor,  by  direction  of  this  board,  and  in  compli- 
ance with  the  directions  of  the  department,  respectfully  to  submit 
the  following  report  and  accompanying  papers,  in  answer  to  the 
resolution  of  the  Senate  of  the  United  States,  calling  upon  the  Secre- 
tary of  the  Treasury  to  communicate  to  the  Senate  the  annual  expense 
of  erecting  light-houses  and  supporting  the  light-house  system  since 
the  creation  of  the  Light-house  Board;  and  also  the  expense  of  the 
same  number  of  years  preceding  the  organization  of  the  said  board. 


253 

The  period  embraced  in  the  clause  of  the  resolution  calling  for  the 
expense  of  erecting  light-houses  and  supporting  the  light-house  sys- 
tem, prior  to  the  organization  of  the  Light-house  Board,  is  5£  years, 
viz:  from  the  commencement  of  the  fiscal  year  on  July  1st,  1847,  to 
the  30th  September,  1852,  inclusive;  and  the  same  period  of  time 
since  the  organization  of  the  Light-house  Board  is  from  October  1, 
1852,  to  December  31,  1857,  inclusive. 

The  table  hereto  appended,  marked  A,  exhibits  the  number  of 
light-houses  and  lighted  beacons;  number  of  light- vessels  and  lights 
on  board  of  them;  expenditures  under  the  several  heads  for  each 
year  and  fraction  of  a  year;  the  mean  average  rates  of  cost  per  annum 
of  the  lights,  and  the  mean  annual  expenditures  on  account  of  the 
buoy  service,  and  the  amount  of  commissions  paid  to  collectors  of 
customs  acting  as  superintendents  of  lights,  for  the  5£  years  imme- 
diately preceding  the  organization  of  the  Light-house  Board. 

Table  B  is  an  exhibition  similar  to  table  A,  for  the  period  of  5£ 
years  under  the  management  of  the  Light-house  Board. 

Table  C  exhibits  the  annual  and  aggregate  special  appropriations 
for  new  aids  to  navigation  on  the  Atlantic,  Gulf,  and  Lake  coasts,  and 
restoring  old  ones,  for  the  period  embraced  in  the  resolutions  of  the 
Senate,  immediately  preceding  the  organization  of  the  Light-house 
Board. 

Table  D  is  the  same  as  table  C,  excepting  that  it  embraces  also 
the  Pacific,  coast,  and  is  for  the  period  embraced  in  the  resolution  of 
the  Senate  since  the  organization  of  the  Light-house  Board. 

Table  E  exhibits  the  amounts  and  balances  of  special  appropria- 
tions on  account  of  new  aids  and  renovating  old  ones,  authorized  by 
Congress,  available  for  those  purposes  on  the  1st  January,  1858,  and 
the  amounts  which  have  reverted  to  the  surplus  fund. 

Table  F  exhibits  the  expenditures  for  the  support  and  maintenance 
of  light-houses  and  buoys  on  the  Pacific  coast  of  the  United  States,  to 
the  31st  December,  1857,  under  the  direction  of  the  Light-house 
Board. 

Table  G  exhibits  the  amount  of  balances  in  the  treasury  and  avail- 
able on  account  of  the  appropriations  for  the  support  and  maintenance 
of  the  light-house  establishment,  at  the  close  of  the  fiscal  year  ending 
June  30,  1857.  and  a  similar  list  of  balances  to  the  31st  of  Decem- 
ber, 1857. 

Table  H  exhibits  a  recapitulation  of  tables  A  and  B,  showing 
means  of  expenditures  per  annum  and  per  light  for  the  two  periods 


254 

of  time  preceding  and  succeeding  the  organization  of  the  Light-house 
Board. 

To  which  is  appended  "List  of  light-houses,  beacons,  and  floating 
lights  of  the  United  States  in  operation  on  the  1st  July,  1851,  <fcc., 
carefully  revised  and  corrected,  by  order  of  Stephen  Pleasanton, 
Fifth  Auditor  and  general  superintendent  of  lights,"  (marked  I,)  and 
"List  of  light-houses,  lighted  beacons  and  floating  lights  of  the 
United  States,  prepared  by  order  of  the  Light-house  Board,  cor- 
rected to  January  1,  1858,"  (marked  J.) 

From  the  tabulated  statements  embraced  in  these  tables,  it  will 
be  seen — 

1.  That  the  mean  annual  average  cost  of  each  light-house  and 
lighted  beacon,  for  the  5|  years  immediately  preceding  the  organiza- 
tion of  the  Light-house  Board,  the  mean  average  cost  of  oil  being, 
for  the  same  period,  $1  13T|¥  per  gallon,  was  $1,302. 

2.  That  the  mean  average  annual  cost  of  each  light-house  and 
lighted  beacon  for  the  5^  years  under  the  management  of  the  Light- 
house Board,    the  mean  annual   cost  of  oil  for  that  period  being 
$1  62rVo  per  gallon,  was  $1,286. 

3.  That  the  annual  average  cost  per  light-house  and  lighted  bea- 
con, under  the  administration  of  the  Light-house  Board,  has  been 
$16  less  than  under  the  previous  management  for  the  same  period  of 
time;  the  difference  in  the  average  cost  of  the  oil  for  illumination  at 
the  same  time  being  $0  49T^  per  gallon  greater  since  the  organiza- 
tion of  the  Light-house  Board  than  for  the  same  period  immediately 
preceding  the  organization  of  the  Board. 

The  325  light-houses  and  lighted  beacons,  existing  at  the  date  of 
the  organization  of  the  Light-house  Board  could  not  have  been 
classed  (according  to  established  denominations,  taking  their  power 
and  range  into  consideration,  in  comparison  with  lights  elsewhere) 
higher  than — 

1  First  class,  or  primary  seacoast  light. 

2  Second  class,  or  secondary  seacoast  lights. 

16  Third  class,  or  bay,  sound,  lake  coast,  &c.,  lights. 
87  Fourth  class,  or  bay,  sound,  river,  and  harbor  lights. 
219  Fifth  and  sixth  class,  or  river,  harbor,  and  pier-head  lights. 

325 


255 

Of  that  number  (325)  there  were— 

One  1st  order  catadioptric  or  Fresnel  apparatus. 

Two  2d       " 

One  3d       " 

One  4th      " 

The  others  (320)  were  fitted  with  inferior  reflectors  and  lamps, 
consuming,  according  to  the  estimates  submitted  to  Congress  for  the 
fiscal  year  ending  June  30,  1852,  (page  65 — A,)  106,365  gallons  of 
oil  per  annum,  as  per  statement,  viz:  Estimates  for  oil,  &c.,  for  fiscal 
year  ending  30th  June,  1852.— (Estimates,  page  65— A.) 

"For  331  light-houses,  3,093  lamps,  35  gallons  each,  108,225  galls." 
From  which  deduct  for  6  reflector  lights,  difference 
between  331  and  325,  at  an  average  of  9  lamps 
each,  54  lamps,  at  35  gallons  each 1,890      " 

Making  total  quantity  for  325  lights 106,365      " 

as  found  by  the  Light-house  Board,  according  to  the  estimates  sub- 
mitted to  the  Department  and  to  Congress. 

Of  the  320  reflector  lights  existing  at  the  time  of  the  organization 
of  the  Light-house  Board  but  six  remain  to  be  fitted,  or  the  apparatus 
provided  for  them,  on  the  catadioptric  system,  which  apparatus  do 
not  deteriorate  from  use  nor  require  to  be  renewed,  producing, 
according  to  the  experience  of  all  countries  into  which  they  have 
been  introduced,  at  least  four  times  as  much  light  for  the  benefit  of 
the  navigator  as  the  best  system  of  reflector  lights  which  has  been 
devised,  and,  at  the  same  time,  at  a  consumption  of  not  more  than 
one-fourth  of  the  quantity  of  oil  required  for  the  best  system  of 
reflector  lights. 

In  illustration  of  the  comparative  merits  and  advantages  of  the  two 
systems  of  light-house  illumination,  (reflectors  in  use  prior  to  the 
organization  of  the  Light-house  Board  and  the  catadioptric  or  lens 
system  nearly  completed  under  the  management  of  the  Light-house 
Board,)  the  following  remark  from  a  recent  publication  of  British 
parliamentary  papers  ' '  On  the  comparative  merits  of  the  catoptric 
and  dioptric  lights  for  light-houses."  may  be  cited: 

"  The  illuminating  power  of  the  most  perfect  kind  of  lenticular 
apparatus  of  the  first  order  and  the  most  perfect  kind  of  parabolic 
reflectors  are  in  the  ratio  of  at  least  eight  to  one." 

In  further  illustration  of  this  subject,  the  estimate  for  oil  for  331 
lights,  submitted  to  Congress  for  the  fiscal  year  ending  June  30,  1852, 


256 

was  108,255  gallons,  (Annual  Estimates,  page  65 — A,)  and  the  esti- 
mates for  the  fiscal  year  ending  June  30,  1853,  for  oil  for  349  lights,  • 
was  114,520  gallons,  (Annual  Estimates,  page  67 — A,)  which  was  at 
least  one-seventh  less  than  the  actual  quantity  required  for  keeping 
efficient  lights,  with  lamps  and  reflectors,  as  may  be  seen  by  refer- 
ring to  the  excess  of  expenditures  over  appropriations,  (table  A,  for 
the  five  and  a  quarter  years  anterior  to  the  organization  of  the  Light- 
house Board,)  and  from  the  fact  that  large  quantities  of  oil  were 
purchased  and  delivered  to  the  different  keepers  by  the  superinten- 
dents, compared  with  the  estimate  for  oil,  (Estimates  for  1858-' 59, 
page  96 — A,)  "for  556  light-houses  and  lighted  beacons,  48,150" 
gallons,  under  the  management  of  the  Light- house  Board. 

During  the  last  four  and  a  quarter  years  the  sum  of  $155,479  07 
has  been  expended  by  the  Light-house  Board  from  the  appropriations 
for  renovations,  repairs,  &c. ,  of  light-houses,  for  the  purchase  of  the 
catadioptric  apparatus  referred  to,  for  the  lights  existing  at  the  time 
the  board  took  charge,  which  was  rendered  indispensable  in  execut- 
ing the  law  of  Congress,  of  March  3,  1851,  and  to  render  the  lights 
efficient,  reliable,  and  economical.  A  deduction  of  this  sum  from  the 
gross  expenses  for  support  and  maintenance  Avould  reduce  the  aver- 
age annual  cost  per  light-house  and  lighted  beacon  under  the  man- 
agement of  the  Light-house  Board,  from  $1,286  to  $1,195,  or  a  differ- 
ence in  favor  of  the  Light -house  Board's  management  over  that  of 
the  five  and  a  quarter  years  previous  to  its  organization  of  $107  per 
annum  per  light,  and  this,  too,  during  a  period  of  time  when  the 
most  important  item  of  light- house  consumption  cost  one-third  more 
than  during  the  previous  period  of  time  with  which  the  comparison 
is  made. 

The  cost  of  other  supplies,  materials,  and  labor  of  all  kinds,  reached, 
during  the  last  five  and  a  quarter  years,  an  equally  great  advance 
over  the  previous  period,  but  which  has  not  been  taken  into  the 
account. 

Another  element  of  legitimate  deduction  in  the  expense  of  main- 
tenance of  the  light-houses,  under  the  Light-house  Board,  but  which 
has  not  been  taken  into  account,  is  the  excess  of  expenditures  of  the 
first  quarter  of  the  fiscal  year  1852-' 53,  immediately  preceding  the 
organization  of  the  Light-house  Board,  in  proportion  to  the  gross  sum 
appropriated  for  the  entire  year,  (table  A,  column  one-quarter  year, 
1852,)  is  the  deficiency  of  supplies  for  the  then  current  year,  ren- 
dering the  purchase  of  21,000  gallons  of  oil,  at  a  cost  of  $26,000,  and 


257 

other  supplies  for  the  lights  indispensable.  Comparing  this  deficiency 
with  the  supplies  on  hand  available  for  the  service  during  the  next 
fiscal  year,  1858-' 59,  under  the  Light-house  Board,  we  find  that  there 
were  in  store,  and  available  for  the  service  of  the  next  fiscal  year, 
at  the  close  of  the  deliveries  for  the  current  year,  35,000  gallons  of 
oil,  and  other  necessary  supplies  in  like  proportion,  which,  if  de- 
ducted from  the  gross  amount  of  money  actually  expended,  would 
greatly  reduce  the  average  annual  cost. 

During  the  existence  of  the  Light-house  Board,  fog  bells  and  other 
fog  signals  have  been  authorized  by  Congress,  including  those  pre- 
viously authorized  but  not  erected,  amounting  to  $58, 900.  The  placing 
of  each  of  these  bells  or  fog  signals  involved  an  expense  of  an  addi- 
tional light  keeper  to  work  it,  or  an  increase  of  the  salary  of  the 
keeper  of  the  light-house  at  which  placed,  for  the  additional  respon- 
sibility and  labor  incurred. 

Lest  it  might  be  inferred  that  the  condition  of  the  towers  and 
buildings,  and  the  reliability  and  powers  of  the  different  lights,  at  the 
time  of  the  organization  of  the  Light-house  Board  and  at  the  present 
time,  were  the  same,  it  is  deemed  proper  to  recur  to  the  number  and 
classes,  or  order,  of  lights  then  and  now. 


1st  order. 

2d  order. 

3d  order. 

4th  order 

5th  and 
6th  order. 

Total. 

Prior  to  Light-house  Board, 

1 

2 

16 

87 

219 

325 

Under  Light-house  Board, 
December  31,   1857  

26 

21 

40 

173 

199 

*459 

4.  In  table  A,  under  the  head  of  light-vessels,  the  mean  annual 
average  cost  per  light  for  the  5|  years  prior  to  the  organization  of 
the  Light-house  Board  is  shown  to  have  been  $2, 749. 

In  table  B,  under  the  head  of  light-vessels,  the  mean  average 
annual  cost  per  light,  for  the  5|  years  under  the  management  of  the 
Light-house  Board,  is  shown  to  be  $2,796.  The  mean  average  cost 
of  oil  purchased  in  the  first  named  period  (table  A)  being  $1  13Tj}¥ 
per  gallon,  and  in  the  latter,  (table  B,)  under  the  Light-house  Board, 
being  $1  6213o!o  per  gallon,  making  an  excess  of  expenditure  per 


0  Of  this  number  six  require  lens  apparatus  to  be  provided. 


17 


258 

light-vessel  light  per  annum,  under  the   management  of  the  Light- 
house Board,  of  $47. 

The  aggregate  amount  of  expenditures  for  support  and  mainten- 
ance of  the  light- vessels,  from  which  the  average  annual  cost  per 
light  is  found,  includes  the  building  of  four  new  light- vessels,  to  take 
places  of  old  ones,  and  of  25  lanterns  and  reflector  apparatus  of  the 
most  approved  description,  for  the  light-vessels  stationed  at  promi- 
nent points  requiring  the  best  lights  that  can  be  produced  from  light- 
vessels,  to  render  the  navigation  of  the  localities  safe  and  easy,  and 
which  expenditures  were  in  addition  to  the  ordinary  repairs,  refit- 
ments, &c.,  which  amount  in  the  aggregate  to  not  less  than  $100,000. 
Of  the  34  light-vessels,  containing  44  lights,  existing  at  the  time 
the  Light-house  Board  took  charge,  there  was  but  one  of  the  1st  class, 
in  tonnage  or  power  of  light,  occupying  a  primary  or  exposed  posi- 
tion; six  of  the  2d  class,  and  the  remainder,  (27,)  occupying  unex- 
posed  positions,  of  small  tonnage,  and  requiring  small  crews  to  take 
charge  of  them. 

Of  the  52  light-vessels,  containing  72  lights,  existing  December 
31,  1857,  under  the  management  of  the  Light-house  Board,  there 
were  11  of  the  1st  class,  of  240  to  275  tons  each,  occupying  exposed 
sea  positions,  requiring  expensive  outfits  of  anchors,  cables,  &c.,  and 
crews  of  about  three  times  the  number  required  by  light-vessels 
occupying  unexposed  positions  in  bays,  sounds,  &c. ;  12  of  the  2d 
class,  and  the  remainder  occupying  unexposed  positions  in  bays, 
sounds,  and  rivers. 

Within  the  last  five  years  the  wages  of  seamen  in  the  navy  has 
been  increased  from  $12  to  $18  per  month,  while  the  rates  in  the 
mercantile  marine,  to  which  the  light-vessel  service  had  mainly  to 
look  for  crews,  ranged  at  still  higher  figures.  Rations  which  cost  in 
1852,  and  prior  to  that  time,  for  the  crews  of  light-vessels,  from  19 
to  20  cents  per  man  per  day,  have  averaged,  during  the  last  five 
years,  from  25  to  35  cents  per  day  per  man.  Labor  and  materials  of 
all  kinds  for  repairing  light-vessels,  and  supplies  other  than  oil,  have 
advanced  in  proportion  to  the  price  paid  for  that  article. 

5.  The  mean  annual  average  cost  of  the  buoy  and  beacon  service, 
(table  A,)  for  the  5£  years  immediately  anterior  to  the  organization 
of  the  Light-house  Board,  was  $75,664  60,  and  for  a  similar  period 
of  time,  under  the  Light-house  Board,  it  was  $82, 267  13.  (Table  B.) 
The  greater  economy  in  this  branch  of  the  light-house  establish- 
ment service,  under  the  management  of  the  Light-house  Board,  will 


259 

be  seen  by  referring  to  the  fact  that,  prior  to  the  organization  of  the 
board,  the  6th  section  of  the  act  making  appropriations  for  light- 
houses, &c.,  approved  September  28,  1850.  which  directs  that  all  the 
buoys  "shall  be  colored  and  numbered"  as  therein  prescribed,  was 
entirely  neglected  and  disregarded  ;  and  that  in  the  general  appro- 
priation bill  for  the  support  and  maintenance  of  lights,  <fec.,  approved 
August  31,  1852,  the  first  appropriation  of  $12,000  was  made  to  carry 
out  that  act  according  to  its  terms. 

The  condition  of  the  beacon  and  buoy  service  at  the  time  of  the 
organization  of  the  Light-house  Board  as  compared  with  its  present 
state,  the  large  increase  in  the  number  and  improvements  in  the 
character  of  those  aids  to  navigation,  authorized  by  Congress  to  be 
placed  since  the  organization  of  the  Light-house  Board,  (table  D, 
column  special  appropriations  for  buoys  and  beacons,  amounting  to 
$448,386  60  during  the  last  5j  years,)  and  disregarding  the  large 
amount  of  property  on  hand  available  for  this  branch  of  the  light- 
house service,  and  which  is  indispensably  necessary  for  its  economical 
and  efficient  management,  the  comparison  will  be  found  to  be  very 
favorable  to  the  last  5|-  years. 

6.  In  the  column  of  table  A,  for  the  mean  annual  average  amount 
paid  to  collectors  of  customs  acting  as  superintendents  of  lights  for 
the  5£  years  anterior  to  the  organization  of  the  Light-house  Board, 
will  be  found  $9,882   11,   and  the  aggregate  amount  for  the  same 
period,  under  the  same  management,  (i.  e.,  prior  to  the  Light-house 
Board,)  $52,358  61. 

In  table  B,  under  the  same  heading,  the  mean  annual  amount  paid 
was  $5,529  52,  and  the  aggregate  amount  paid  under  the  manage- 
ment of  the  Light-house  Board  was  $28,847  66,  making  an  annual 
saving,  under  the  Light-house  Board,  of  $4,352  59,  and  an  aggregate 
saving  for  the  5£  years  of  $23,510  95. 

7.  Table  F  exhibits  the  expenditures  under  the  different  heads  of 
appropriation  for  the  light-house  service  on  the  Pacific  coast.     The 
appropriations  for  that  coast  have  been  made  upon  estimates  distinct 
from  those  for  the  Atlantic,  Gulf,  and  Lake  coasts,  and  as  there  were 
no  aids  on  that  part  of  the  coast  of  the  United  States  existing  at  the 
time  of  the  organization  of  the  Light-house  Board,  there  were  no 
prior  expenses  to  be  compared  with  them.     The  great  distance  from 
the  Atlantic  to  that  coast,  and  the  difficulties  and  expenses  attending 
the  distribution  of  supplies  to  the  lights  there,  render  it  necessary  to 
keep  a  larger  proportional  supply  of  oil,  &c.,  in  store  for  future  use 


260 

than  on  the  Atlantic  side.  The  cost  of  labor,  materials,  and  supplies 
of  all  kinds  has  been,  and  is  yet,  three  to  five  times  what  it  is  on  the 
Atlantic  coast,  while  the  average  rate  of  compensation  of  light-house 
keepers  has  been  fixed  by  Congress  at  double  the  rate  on  the  Atlantic 
coast. 

8.  Table  C  exhibits  the  amounts  of  appropriations,  under  the  re- 
spective heads,  for  new  aids  to  navigation,  and  for  renewing  old  ones, 
made  by  Congress  in  special  bills,  from  March  3,  1847,  to  August  31, 
1852,    and    prior   to   the   organization   of   the    Light-house   Board, 
amounting  in  the  aggregate  to  $2,541,862  66. 

Of  those  appropriations  a  number  of  the  works  remained  to  be 
completed,  commenced,  or  condemned  under  the  law  as  unnecessary, 
by  the  Light-house  Board  at  the  time  it  was  organized. 

9.  Table  D  exhibits  the  amounts  of  appropriations,  under  the  re- 
spective heads,  for  new  aids  to  navigation  and  for  renewing  old  ones, 
specially  authorized  by  Congress,   from  March  3,  1853,  to  March  3, 
1857,  and  during  the  existence  of  the  Light-house  Board,  amounting 
to  $3,636,930  72.     Of  these  sums  the  appropriations  made  respect- 
ively on  the  3d  of  March,  1853,  1855,  1857,  amounting  in  the  aggre- 
gate to  $922,467  03,  were  based  upon  estimates  in  the  annual  esti- 
mates submitted  by  this  board,  and  included  by  the  Secretary  of  the 
Treasury  in  the   annual   estimates   submitted  by  him  to   Congress. 
Those  for  the  years  1854  and  1856,  amounting  in  the  aggregate  to 
$2,714,463  69,  were  embraced  in  special  light-house  appropriation 
bills,  originating  with  the  Committees  on  Commerce  of  Congress. 

10.  Table  E  shows  the  sum  of  $1,756,205  81  unexpended,  includ- 
ing $369,597  90  carried  or  to  be  carried  to  the  surplus  fund  of  the 
treasury,  and  $1,356,200  63  available  on  account  of  special  light- 
house works  authorized  by  Congress. 

11.  Table  G  shows  at  the  close  of  the  last  fiscal  year  a  total  bal- 
ance in  the  treasury  of  $467,015  49,  exclusive  of  sums  in  the  hands 
of  disbursing  officers  available  for  the  support  and  maintenance  of 
the   light-house   service    during  the    current   year,   and  being  that 
amount  less  than  the  sum  appropriated  or  available  for  the  general 
service,  and  also  a  balance  at  the  close  of  the  half  of  the  current  fiscal 
year  (December  31,  1857)  of  $967,106  15  available  for  the  remaining 
half  and  for  the  next  year's  service  in  maintaining  the  light-house 
establishment. 

12.  The  table  H  is  a  recapitulation  of  the  averages  for  the  two 
periods  of  five  and  a  quarter  years  each,  both  before  and  since  the 


261 

organization  of  the  Light-house  Board,  prepared  from  the  tables 
before  recited. 

13.  The  two  light-house  lists,  July  1.  1851,  and  December  31, 
1857,  will  afford  a  general  comparative  view  of  the  service  at  the 
two  periods  of  time,  and  the  columns  of  "built,"  "rebuilt,"  "refit- 
ted," of  the  latter  will  show  in  brief  what  has  been  done  towards 
rendering  the  lights  efficient  and  reliable  by  the  Light-house  Board. 

It  may  not  be  amiss  to  add  that  the  light-houses,  lighted  beacons, 
and  light-vessels,  authorized  prior  (but  not  built)  and  those  author- 
ized since  the  organization  of  the  Light-house  Board,  amount  in  the 
aggregate  to  near  300;  permanent  beacons  about  80;  and  the  buoys 
have  been  increased  within  the  same  period  nearly  or  quite  four-fold. 

The  Light-house  Board,  in  submitting  its  estimates,  for  the  first 
time,  (November  10,  1852,)  for  the  support  of  the  light-house  estab- 
lishment for  the  fiscal  year  ending  June  30,  1854,  states,  in  the  letter 
accompanying  them :  ' '  The  estimates  of  this  board  for  the  fiscal  year 
ending  June  30,  1854,  are  the  same  in  every  respect  as  those  for 
1852,  1853,  for  the  same  objects.  The  additional  estimates  for  ob- 
jects authorized  by  the  acts  of  March  3,  1851,  and  August  31,  1852, 
not  contained  in  former  lists  and  estimates,  are  based  upon  the  same 
data,  and  bear  relatively  the  same  proportion  to  them. 

"The  additional  estimates  submitted  for  objects  deemed  of  import- 
ance are  not  such  as  have  hitherto  been  classed  under  the  ordinary 
heads  of  repairs,  &c.,  and  amount  in  the  aggregate  to  $27,000  less 
than  the  estimates  for  similar  objects  last  year. 

' '  For  support  of  the  light-houses  and  other  aids  to  navigation  on 
the  coasts  of  California  and  Oregon,  estimates  are  now  submitted  for 
the  first  time. 

"The  continued  high  prices  of  labor,  <fcc.,  on  the  Pacific  coast  ren- 
dered it  necessary  that  a  different  scale  of  estimating  should  be 
adopted  for  that  coast ;  but  in  doing  so  the  board  has  conformed  its 
estimates  to  the  most  economical  rates  which  would  seem  to  be  justi- 
fied by  the  best  information  that  could  be  obtained.''' 

The  letter  of  the  Light-house  Board  of  October  7,  1857,  addressed 
to  the  Secretary  of  the  Treasury,  submitting  estimates  for  the  support 
of  the  light-house  establishment  for  the  fiscal  year  ending  June  30, 
1859,  states: 

"These  estimates  have  been  prepared  to  meet  the  actual  state  of 
the  light-house  service  as  it  will  be  at  the  close  of  the  present  fiscal 
year,  and  not  upon  the  pro-rata  of  expenditures  of  previous  years,  as 


262 

heretofore,  in  view  of  the  fact  that  by  the  commencement  of  the  next 
fiscal  year  the  system  of  catadioptric  illumination  authorized  by  the 
7th  section  of  the  act  of  Congress  making  appropriations  for  light- 
houses, &c.,  approved  March  3,  1851,  and  which  has  been  in  steady 
progress  of  execution  since  the  organization  of  this  board  on  the  9th 
October,  1852,  will  be  near  its  full  completion,  which  will  thence- 
forth produce  the  economical  results  indicated  at  that  time  by  greatly 
diminishing  the  annual  consumption  of  oil,  wicks,  chimneys,  and 
other  supplies,  as  compared  with  that  of  the  old  system  of  reflectors 
and  lamps,  in  addition  to  other  benefits  arising  from  increased  bril- 
liancy and  power  of  the  lights  and  from  illuminating  apparatus  which 
is  not  liable  to  any  sensible  deterioration  from  use. 

The  aggregate  amount  of  estimates  submitted  for  the 
fiscal  year  ending  June  30,  1859,  for  the  Atlantic, 
Gulf,  and  Lake  coasts,  is • $712,598  99 

The  aggregate  amount  of  estimates  for  the  Pacific  coast 

for  the  fiscal  year  ending  June  30,  1859 78,535  91 


The  aggregate  amount  of  estimates  for  the  fiscal  year 
ending  June  30,  1859,  for  the  Atlantic,  Gulf,  Lake, 
and  Pacific  coasts,  is $791, 134  90 


Showing  a  diminution  of $399,471  39 

in  the  estimates  for  the  fiscal  year  ending  June  30,  1859." 

The  estimates  for  annual  expenditures  for- support  and  maintenance 
of  the  light-house  establishment,  under  the  management  of  the  Light- 
house Board,  for  the  five  fiscal  years  ending  June  30,  1858,  have 
been  made  at  the  same  rate  as  that  for  the  fiscal  year  ending  June 
30,  1853.  The  letters  accompanying  the  estimates  from  year  to  year 
show  this.  In  every  case  the  existing  light-houses,  and  those  au- 
thorized to  be  built,  were  included.  The  object  of  this  was  to  com- 
plete the  renovation  of  the  light-houses,  and  their  equipment  with 
Fresnel  lenses,  as  soon  as  practicable,  without  asking  Congress  for 
special  appropriations  for  the  purpose. 

By  the  end  of  the  present  fiscal  year  that  object  will  have  been 
accomplished,  and  it  will  be  seen,  from  the  letter  of  the  board,  of 
October  7,  1857,  previously  quoted,  that  the  estimates  for  the  fiscal 
year  ending  June  30,  1859,  are  based  upon  the  saving  made  by  the 
introduction  of  the  lens  system,  and  are  the  first  fruits  of  that  system, 
so  far  as  regards  an  annual  diminution  of  the  expense  of  the  estab- 


263 


lishment,  the  benefits  of  the  introduction  having  been  felt  in  all  other 
respects  since  its  commencement.  A  further  diminution  in  the  esti- 
mates may  confidently  be  expected  for  the  fiscal  year  ending  June 
30,  1860,  when  it  is  hoped  that  the  expenditures  will  be  brought  to 
the  minimum. 

Notwithstanding  the  fact  that  large  expenditures  for  rebuilding 
light-houses  and  purchasing  new  illuminating  apparatus  have  been 
made  from  the  general  fund  for  support  and  maintenance,  it  will  ap- 
pear, by  a  comparison  of  the  two  periods  of  5^  years  before  and  after 
the  organization  of  the  Light-house  Board,  that  in  the  former  period 
the  expenditures  overran  the  appropriations  by  $127,421  79,  (a  defi- 
ciency made  good  by  transfers  from  special  appropriation  for  light- 
houses,) while  in  the  latter  the  appropriations  exceeded  the  expen- 
ditures by  $590,176  18. 

Inasmuch  as  the  subjects  relating  to  light-houses,  illumination,  the 
management  of  the  light-house  service  of  this  and  other  maritime 
countries,  &c.,  were  much  discussed  in  Congress,  from  about  1838  to 
the  passage  of  the  law  authorizing  the  organization  of  the  Light- 
house Board  in  1852,  for  a  general  view  of  the  condition  of  the  light- 
house establishment  prior  to  the  latter  date  the  board  would  respect- 
fully refer  to  the  following  congressional  documents,  being  a  part 
only  of  those  printed  : 

Senate  document  No.  138,  2d  session,  25th  Congress. 

Senate  document  No.  258,  2d  session,  25th  Congress. 

Senate  document  No.  159,  2d  session,  25th  Congress. 

Senate  document  No.  506,  2d  session,  25th  Congress. 

Senate  document  No.  474,  1st  session,  26th  Congress. 

Senate  document  No.  619,  1st  session,  26th  Congress. 

Senate  document  No.  488,  1st  session,  29th  Congress. 

Senate  executive  document  No.  28,  1st  session,  32d  Congress, 
pages  18  to  20,  et  seq. 

Senate  executive  document  No.  22,  2d  session,  32d  Congress, 
pages  70.  et  seq. 

House  document  No.  24,  3d  session,  25th  Congress,  page  2,  (oil 
tests,  &c.,)  and  pages  48,  69,  70,  71,  et  seq.,  and  113. 

House  document  No.  183,  2d  session,  27th  Congress. 

House  executive  document  No.  114,  1st  session,  32d  Congress, 
and  also,  for  a  general  view  of  the  condition  of  the  light-house  ser- 
vice, under  the  management  of  the  Light-house  Board,  to  the  several 
reports  on  the  finances,  submitted  by  the  Treasury  Department  to 


264 

Congress,  for  1853-' 54-' 55-' 56,   and  to  the  report  No.   16  in  the 
finance  report  of  December,  1857,  from  page  229. 

It  is  respectfully  submitted  that  the  foregoing  report  and  accom- 
panying tables  show  the  following  facts  : 

1.  The  whole  system  has  been  remodelled  according  to  the  tenor 
of  the  7th  section  of  the  act  of  Congress  of  March  3,  1851,  producing 
the  effects  contemplated  by  that  act  with  regard  to  economy  and 
efficiency. 

2.  The  number  of  buoys,  beacons,  and  other  day  marks,  has  been 
increased  by  direction  of  Congress  at  least  four-fold. 

3.  The  number  of  light  stations,    since   the   organization  of  the 
Light-house  Board,  has,  under  the  authority  of  Congress,  been  nearly 
doubled. 

4.  For  the  imperfect  lamps  and  lanterns  previously  employed  new 
apparatus  has  been  introduced,  the  most  perfect  in  character  which 
the  science  and  skill  of  the  present  day  are  able  to  afford. 

5.  Not  only  has  a  large  diminution  of  the  amounts  of  oil  and  other 
supplies  for  lights  been  effected,  but  the  extent  to  which  the  seacoast 
lights  are  visible   over  the   surface  of  the  water  has  been  greatly 
increased,  which  increase  was  indispensable  for  the  safety  of  navi- 
gation. 

6.  From  the  combined  results  of  these  changes,  the  efficiency  of 
the  system  has  been  multiplied  eight  times,  at  a  nominal  aggregate 
annual  increase,  the  expenditures  per  light  having  been  actually  less 
than  they  were  before  the  organization  of  the  board. 

7.  This  efficiency  may  be  still  further  increased  with  an  annual 
reduction  of  the  expenditures,  since  the  cost  of  the  introduction  of 
the  new  apparatus  was  much  greater  than  that  which  will  be  required 
to  continue  its  use. 

Very  respectfully, 

W.  B.  SHUBRICK, 
Chairman  of  the  Light-house  Board. 
THORNTON  A.  JENKINS,  )  c, 
W.  B.  FRANKLIN.  [  Secretaries. 

Hon.  Ho  WELL  COBB, 

Secretary  of  the  Treasury. 


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267 

TABLE  C. 

(ATLANTIC,  GULF,  AND  LAKE  COASTS.) 

Exhibiting  the  amounts  appropriated,  by  Congress  in  special  appropriation- 
bills,  reported  from  the  Committees  on  Commerce  and  in  the  general  appro- 
priation bills  for  light-houses  at  neio  localities,  rebuilding  old  light-houses, 
light-vessels  for  new  localities,  and  rebuilding  light-vessels,  occupying  old 
stations  ivhich  required  rebuilding,  Sfc.,  for  the  Jive  years  ^1847—1852^  imme- 
diately preceding  the  organization  of  the  Light-house  Board. 


Date  of  approval  of  appropri- 
ation bills. 

Amountappropria- 
ted  for  new  light- 
houses   and    re- 
building old  ones. 

Amount  appropria- 
ted for  new  light- 
vessels    and    re- 
building old  ones. 

Amount  appro- 
priated for  fog 
bells,  &c. 

Total. 

March  3,  1847  

$521,250  00 

$25,000  00 

$546,250  00 

August  12  and  14,  1848. 
March  3    1849 

252,091  90 
191  441  37 

64,000  00 
35  407  00 

$750  00 
750  00 

316,841  90 
227,598  37 

September  28,  1850  
March  3,  1851  

422,590  00 
314,432  39 

8,000  00 
42,500  00 

5,500  00 
250  00 

436,090  00 
357,  182  39 

August  31,  1852 

495  200  00 

130,200  00 

32,500  00 

657,900  00 

2,197,005  66 

305,107  00 

39,750  00 

2,541,862  66 

THORNTON  A.  JENKINS, 
W.  B.  FRANKLIN, 


W.  B.  SHUBRICK,  Chairman. 
Secretaries. 


TREASURY  DEPARTMENT, 

Office  Light-house  Board,  March  13,  1858. 


268 
TABLE  D. 

(ATLANTIC,  GULF,  LAKE,  AND  PACIFIC  COAST.) 

Exhibiting  the  amounts  of  special  appropriations  made  b  i/  Congress  for  erect- 
ing light-houses  at  new  localities,  rebuilding  old  ones,  building  light-vessels 
for  new  localities,  fyc.,  and  for  buoys,  beacons,  and  fog  bells  for  new  localities, 
and  restoring  those  destroyed,  for  the  five  years  f  1852  to  1857^  immediately 
succeeding  the  organization  of  the  Light-house  Board. 


iijjs         14 

if* 

m 

Date  of  approval 
appropriation  of 

Q.V  a~o 

51  il 

l|. 

Irs 

l>  u  . 

fill 

Total. 

jij] 

lit 

||J! 

111! 

March    3,  1853. 

$276,250  00 

$28,000  00 

$6,000  00 

$43,  160  00 

$353,410  00 

August  3,  1854. 

1,210,338  00 

33,500  00 

19,600  00 

239,640  00 

1,503,078  00 

March   3   1855 

245  000  00 

245  000  00 

Aug.     18,  1856. 

1,054,514  15 

42,597  54 

800  00 

113,474  00 

1,211,385  69 

March    3,1857.        231.83881 

-40,105  62 

°52,  112  60 

324,057  03 

3,017,940  96 

144,203  16 

26,400  00 

448,386  60 

3,636,930  72 

°To  repair  damages  and  supply  losses  occasioned  by  ice  caused  by  storm  of  January  19, 
1857. 


THORNTON  A.  JENKINS, 
W.  B.  FRANKLIN, 


W.  B.  SHUBRICK,   Chairman. 
>  Secretaries. 


TREASURY  DEPARTMENT, 

Office  Light-house  Board,  March  13,  1858. 


TABLE  E. 

Exhibiting  the  amounts  of  special  appropriations  which  were  available  on  Jan- 
uary 1,  1858,  and  of  those  which  have  reverted,  or  will  revert,  to  the  surplus 
fund,  under  the  administration  of  the  Light-house  Board. 

Balance  on  account  of  light-houses $1,356,200  63 

Balance  on  account  of  buoys  and  beacons 30,407  28 

Amount  carried  to  surplus  fund 369,597  90 


Total. 


1,756,205  81 


W.  B.  SHUBRICK,   Chairman. 

THORNTON  A.  JENKINS,  )  0  . 

W.  B.  FRANKLIN,  }  Secretaries. 


TREASURY  DEPARTMENT, 

Office  Light-house  Board,  March  13,  1858. 


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272 


ST.  CHERON,  (SEINE  &  OISE,) 

May  7,  1861. 

SIR  :  I  was  about  leaving  Paris,  some  three  weeks  ago,  to  locate 
myself  in  the  country,  where  I  pass  the  best  part  of  the  year,  when 
I  received  the  Report  on  Finances  of  the  United  States  of  1858,  as 
well  as  the  very  obliging  letter  with  which  you  transmitted  the  doc- 
ument. I  was  then  suffering  from  an  attack  of  pleurisy,  and  my  con- 
valescence was  retarded  by  several  accidents.  This  circumstance, 
joined  to  the  many  embarrassments  inseparable  from  a  change  of 
residence,  will  be  my  excuse  fgr  not  having  earlier  expressed  my 
lively  thanks.  §  So  soon  as  I  was  sufficiently  restored  to  health  I 
perused  the  important  documents  which  you  sent  me,  being  attracted 
particularly  by  the  chapters  in  relation  to  the  light-house  service. 
The  prodigious  development  of  this  service  within  so  short  a  time, 
under  the  Light-house  Board,  has  truly  astonished  me.  My  old  ex- 
perience, in  fact,  enables  me  the  better  to  appreciate  how  much 
energy  and  activity  were  necessary  to  bring  to  this  degree  of  perfec- 
tion the  light-house  service  of  such  a  vast  expanse  of  coast — as  well 
on  the  Pacific  as  on  the  Atlantic — without  mentioning  the  task  of 
succeeding  in  establishing,  against  hostile  prejudices,  the  adoption  of 
a  new  system.  Much  is  due  to  you,  sir,  and  to  your  honorable  co- 
laborateurs,  for  having  created  in  so  short  a  time  this  magnificent 
and  combined  establishment,  and  you  should  congratulate  yourself 
that,  thanks  to  your  activity,  the  Union,  ivherein  is  strength,  and 
which  I  find  now  so  fatally  compromised  by  the  blindest  passions,  has 
not  been  overthrown  before  the  accomplishment  of  your  philanthropic 
work.  I  hope,  however,  that  reason  will  yet  triumph  over  these 
retrograde  ideas,  and  that  Providence  will  listen  to  the  prayers  of 
all  generous  hearts  by  maintaining  the  most  admirable  political  struc- 
ture which  has  ever  been  erected  by  the  genius  of  liberty. 

Excuse,  dear  sir,  this  digression  upon  the  seething  volcano  of  your 
national  politics,  and  be  pleased  to  accept  the  renewed  assurance  of 
my  high  esteem,  as  well  as  of  my  sentiments  of  great  devotion. 

LEONOR  FRESNEL. 

To  Com'  r  THORNTON  A.  JENKINS,  U.  S.  Navy, 
Secretary  of  the  Light-house  Board, 

Washington  city,   U.  S.  A. 

FINIS. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 

Los  Angeles 


i 


U.S.  Light-house 


377  board  - 

U53p  Papers  on  the  com- 


parative  merits  of 
the  catoptric  and  diop^ 
trie  or  cat^dioptric 


TC 

377 

U58p 


000737759  1 


jagHfl 


in 


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